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Round-to-Rectangular Tube Adapter STL file ⌀80 mm to 80×80 mm, thickness 3 mm

Tube STL file OD 24 mm, ID 20 mm, length 100 mm

Rectangular-base box with lid STL file – 250×90×25 mm, wall thickness 3 mm

Square-base box with lid STL 3D model – 70×70×40 mm, wall thickness 4 mm

Small parts organizer with 6 drawers 40×15×30 mm STL 3D file, thickness: 2 mm

Multi-compartment box STL 3D file: 6 compartments of 80×20×20 mm

Hollow tube STL 3D model OD 60 mm, ID 58 mm, length 100 mm

Tube adapter STL file ⌀ 60–30 mm (Length: 140 mm)

Enclosure with screw-mounted lid STL file: 100×100×20 mm (with ventilation on the lid and under the enclosure)

Pipe clip holder Ø50 mm STL file · Countersunk screw Ø5 mm

Browse a growing library of free STL files and 3D models — or generate custom parts online to your exact specs.

Featured Model of the Day

Color-coded compartment box STL 3D file: 16 compartments of 25×25×25 mm 📦 #1196

3 object(s) - format STL

View of object #0

Latest user-generated 3D models

Rectangular box with lid STL file – 120×70×80 mm, wall thickness 4 mm 📦 #9908

2 object(s) - format STL

View of object #0

From the Blog

Why Modeling Strategy Matters in Procedural CAD Modeling

2025-12-14 · 3D Modeling · sylvain

Why does modeling strategy matter so much in procedural CAD? Two scripts can produce the exact same geometry while showing very different generation times.

Using a concrete build123d example, this article explains why certain operations, such as fillets, become expensive when repeated at scale, and how a simple change in approach can drastically reduce computation time.

A clear overview of the key challenges in procedural modeling, highlighting the direct impact of design choices on CAD engine performance.

Read the article

A selection of custom 3D models

📦 Model #4476

1 object(s)

- format STL

Tubing adapter STL 3D file ⌀ 40–37 mm (Length: 115 mm)

Tube adapter ⌀40 mm to ⌀37 mm in STL 3D format. Length of this connector is 115 mm. The thickness of the tubes is identical: 5 mm. The larger-diameter tube has a sleeve length of 35 mm, the smaller one of 40 mm. The ends are rounded to facilitate the connection of the two tubes.

Parameter	Value	Unit
side A length	35	mm
side A outer diameter	40	mm
side A thickness	5	mm
side B length	40	mm
side B outer diameter	37	mm
side B thickness	5	mm
transition length	40	mm
axis offset	0	mm
ends fillet	fillet on bo...

📦 Model #2906

1 object(s)

- format STL

Tube adapter STL file ⌀ 20–7 mm (Length: 26 mm)

Tube reducer ⌀20 mm to ⌀7 mm in STL format. Total length of this adapter is 26 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a length of 8 mm, the smaller one of 8 mm as well. The ends are rounded.

Parameter	Value	Unit
side A length	8	mm
side A outer diameter	20	mm
side A thickness	2	mm
side B length	8	mm
side B outer diameter	7	mm
side B thickness	2	mm
transition length	10	mm
axis offset	0	mm
ends fillet	fillet on bo...

📦 Model #1884

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀152.4 mm to 200×60 mm, thickness 3 mm + offset

3D model in STL format of a round-to-rectangular tube adapter with an external diameter of ⌀152.4 mm and a rectangular section with inner dimensions 200×60 mm. The wall thickness is 3 mm and the total length is 200 mm. The adapter has an offset of 60 mm along the Z axis.

Parameter	Value	Unit
cylinder outer diameter	152.4	mm
cylinder inlet length	30	mm
rectangle internal length	200	mm
rectangle internal height	60	mm
rectangle inlet length	30	mm
offset Z	60	mm
offset Y	0	mm
total length	200	mm
thickness	3	mm
chamfer	no chamfer

📦 Model #2390

1 object(s)

- format STL

Round air vent STL 3D file ∅ 115 mm, slat angle: 45°

3D file of a round grille for air circulation in STL format. Its male diameter is 115 mm. The slats have an angle of 45° and a high thickness of 2 mm. This ventilation grille has a collar of 10 mm. The full diameter of this model is 135 mm.

Parameter	Value	Unit
male diameter	115	mm
slat angle	45	°
slat thickness	2	mm
flange width	10	mm
central reinforcement	no

📦 Model #4503

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 125–80 mm (Length: 105 mm)

Straight tube coupler ⌀125 mm to ⌀80 mm in STL format. Total length of this junction is 105 mm. The thickness of the tubes is identical: 5 mm. The larger-diameter tube has a sleeve length of 35 mm, the smaller one of 40 mm. The ends are raw.

Parameter	Value	Unit
side A length	35	mm
side A outer diameter	125	mm
side A thickness	5	mm
side B length	40	mm
side B outer diameter	80	mm
side B thickness	5	mm
transition length	30	mm
axis offset	0	mm
ends fillet	no fillet

📦 Model #3473

1 object(s)

- format STL

Pot STL 3D file, inner: base Ø49 mm, top Ø49 mm, height 40 mm - wall thickness 1 mm

File of a pot in STL 3D format. This model can be used for storing small parts in a workshop or on a desk. The sides are vertical, providing a constant inner volume, with a inner height of 40 mm and an identical inner diameter at the top and bottom of 49 mm. The overall height of the bowl is 41 mm.

Parameter	Value	Unit
inner bottom diameter	49	mm
inner top diameter	49	mm
inner height	40	mm
wall thickness	1	mm

📦 Model #1788

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 152–52 mm (Length: 180 mm)

Tube reducer ⌀152 mm to ⌀52 mm in STL format. Length of this connector is 180 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a length of 20 mm, the smaller one of 40 mm. The two axes of the tubes are offset by 35.9 mm. The ends are not rounded.

Parameter	Value	Unit
side A length	20	mm
side A outer diameter	152	mm
side A thickness	2	mm
side B length	40	mm
side B outer diameter	52	mm
side B thickness	2	mm
transition length	120	mm
axis offset	35.9	mm
ends fillet	no fillet

📦 Model #2034

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀112 mm to 290×80 mm, thickness 3 mm

3D model in STL format of a round-to-rectangular adapter with an external diameter of ⌀112 mm and a rectangular section with internal dimensions 290×80 mm. The wall thickness is 3 mm and the overall length is 300 mm. A chamfer is applied on the outside of the cylindrical end to ease insertion.

Parameter	Value	Unit
cylinder outer diameter	112	mm
cylinder inlet length	70	mm
rectangle internal length	290	mm
rectangle internal height	80	mm
rectangle inlet length	50	mm
offset Z	0	mm
offset Y	0	mm
total length	300	mm
thickness	3	mm
chamfer	chamfer on t...

📦 Model #4497

1 object(s)

- format STL

Tubing adapter STL 3D file ⌀ 32–19 mm (Length: 65 mm)

Tube fitting ⌀32 mm to ⌀19 mm in STL 3D format. Length of this junction is 65 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a sleeve length of 35 mm, the smaller one of 20 mm. The ends are not rounded.

Parameter	Value	Unit
side A length	35	mm
side A outer diameter	32	mm
side A thickness	2	mm
side B length	20	mm
side B outer diameter	19	mm
side B thickness	2	mm
transition length	10	mm
axis offset	0	mm
ends fillet	no fillet

📦 Model #3502

1 object(s)

- format STL

Protective grid STL 3D file, 60x60mm, mesh: 8mm

Download this 3D square honeycomb grid model in STL format. The overall size is 60x60 mm, with wide 8 mm cell size for optimal air circulation. This type of grid serves both protection and ventilation roles.

Parameter	Value	Unit
length or center-to-center	60	mm
width or center-to-center	60	mm
mesh size	8	mm
dual color	no
holes	no

📦 Model #4201

1 object(s)

- format STL

Washer / Flat Gasket STL 3D file ⌀ID: 3.9 mm ⌀OD: 6.9 mm thickness: 4.3 mm

3D model of washer / gasket in STL 3D file format. This part features an inner diameter of ⌀3.9 mm and an outer diameter of ⌀6.9 mm. The total thickness is 4.3 mm. This part has no finish applied.

Parameter	Value	Unit
inner diameter	3.9	mm
outer diameter	6.9	mm
thickness	4.3	mm
finish	none

📦 Model #1483

1 object(s)

- format STL

Tube adapter STL file ⌀ 200–50 mm (Length: 80 mm)

Tube reducer ⌀200 mm to ⌀50 mm in STL 3D format. Total length of this junction is 80 mm. The thickness of the tubes is identical: 3 mm. The larger-diameter tube has a sleeve length of 30 mm, the smaller one of 30 mm as well. The ends have no fillet.

Parameter	Value	Unit
side A length	30	mm
side A outer diameter	200	mm
side A thickness	3	mm
side B length	30	mm
side B outer diameter	50	mm
side B thickness	3	mm
transition length	20	mm
axis offset	0	mm
ends fillet	no fillet

📦 Model #1671

2 object(s)

- format STL

Enclosure with screw-mounted lid STL file: 158×110×60 mm (with ventilation under the enclosure)

Download this enclosure with a screwed lid in 3D STL format. The dimensions are 158 mm long by 110 mm wide and 60 mm high. The cover is 19 mm high. Side thickness is 4 mm. This enclosure features marked cooling area under the base.

Parameter	Value	Unit
length	158	mm
width	110	mm
total height	60	mm
lid height	19	mm
wall thickness	4	mm
screw margin	-0.1	mm
fit clearance	0.1	mm
cooling level	5
cooling zone(s)	cutouts on t...

📦 Model #4396

1 object(s)

- format STL

Honeycomb grid STL file, 250x250mm, mesh: 10mm

Square grid model as a STL file. The overall size is 250x250 mm, with very large 10 mm cell size for maximum airflow. This grid serves as both a protective guard and a ventilation panel.

Parameter	Value	Unit
length or center-to-center	250	mm
width or center-to-center	250	mm
mesh size	10	mm
dual color	no
holes	no

📦 Model #4447

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 100–79 mm (Length: 240 mm)

Straight tube fitting ⌀100 mm to ⌀79 mm in STL 3D format. Total length of this sleeve is 240 mm. The larger-diameter tube has a thickness of 4 mm and a sleeve length of 100 mm. The smaller-diameter tube has a thickness of 5 mm and a length of 100 mm as well. The axes of the tubes are offset by 11.4 mm. The ends feature an external fillet.

Parameter	Value	Unit
side A length	100	mm
side A outer diameter	100	mm
side A thickness	4	mm
side B length	100	mm
side B outer diameter	79	mm
side B thickness	5	mm
transition length	40	mm
axis offset	11.4	mm
ends fillet	fillet on th...

📦 Model #3550

1 object(s)

- format STL

O-ring STL file ID 55 × CS 10 mm

3D model in STL format of O-ring (torus-shaped seal) with Internal diameter (ID) 55 mm × section thickness 10 mm. Outer diameter (OD) resulting is therefore 75 mm.

Parameter	Value	Unit
inner diameter (ID)	55	mm
cross section (CS)	10	mm

📦 Model #3057

1 object(s)

- format STL

Right-angle bracket 150×150 mm STL 3D file, thickness 6 mm, hole diameter 6 mm

3D file of a mounting bracket with a central reinforcement in STL format. The dimensions are 150 mm in length, 150 mm in height, 14 mm in width, and 6 mm in thickness. The screw holes are designed with a diameter of 6 mm. Chamfers are applied to the holes to improve the seating of the heads. The central reinforcement bar reduces bending and provides two clearances for screwdriver access. No support is needed to print this bracket, printed flat on the build plate.

Parameter	Value	Unit
length	150	mm
height	150	mm
width	14	mm
thickness	6	mm
hole diameter	6	mm
chamfer on the holes	yes

📦 Model #1429

1 object(s)

- format STL

Round air vent STL file ∅ 55 mm, slat angle: 30° with central reinforcement

3D model of a round air vent for ventilation in STL format. Its insertion diameter measures 55 mm. The slats have a slight angle of 30° and a low thickness of 1.6 mm. A centered vertical reinforcement strengthens the slats. This vent grille features a prominent flange of 20 mm. The overall diameter of the model is 95 mm.

Parameter	Value	Unit
male diameter	55	mm
slat angle	30	°
slat thickness	1.6	mm
flange width	20	mm
central reinforcement	yes

📦 Model #1701

1 object(s)

- format STL

Washer / Flat Gasket STL file ⌀ID: 26 mm ⌀OD: 40 mm thickness: 12 mm + chamfers

Download this 3D file of flat gasket / washer in STL format. This part features an inner diameter of ⌀26 mm and an outer diameter of ⌀40 mm. The thickness is 12 mm. Chamfers are present on both the inner diameter and the outer diameter, each with a value of 1.5 mm. These finishes are applied on both sides.

Parameter	Value	Unit
inner diameter	26	mm
outer diameter	40	mm
thickness	12	mm
finish	chamfer
finish position	inner + oute...
sides	two sides
finish value	1.5	mm

📦 Model #2150

2 object(s)

- format STL

Small parts organizer with 6 drawers 40×150×140 mm STL file, thickness: 2 mm

3D model of storage drawers in 3D STL format. This model includes 6 drawers, arranged in 1 rows and 6 columns. Specifically, this means 1 rows of 6 drawers. Each drawer offers a storage volume of 40 mm wide, 150 mm high, and 140 mm deep. The wall thickness is 2 mm. The overall dimensions of the box measure 281 x 156.5 x 146 mm. All the objects in this model are intended to be printable without support generation.

Parameter	Value	Unit
number of rows	1
number of columns	6
inner drawer depth	140	mm
inner drawer width	40	mm
inner drawer height	150	mm
wall thickness	2	mm
removable divider	none

📦 Model #4414

2 object(s)

- format STL

Round box with lid STL 3D file ⌀ 134 mm - Height: 20 mm, Shell: 2 mm

Get this circular box model in 3D STL format. Its diameter is 134 mm and its total height is 20 mm. The wall thickness is 2 mm. A fillet located at the bottom of the box makes it easier to grip objects.

Parameter	Value	Unit
external diameter	134	mm
total height	20	mm
wall thickness	2	mm
fit clearance	0.2	mm
inner bottom fillet	1	mm

📦 Model #4475

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 40–37 mm (Length: 118 mm)

Straight tube fitting ⌀40 mm to ⌀37 mm in STL format. Total length of this connector is 118 mm. The thickness of the tubes is identical: 5 mm. The larger-diameter tube has a sleeve length of 38 mm, the smaller one of 40 mm. The ends have a fillet to make tube connection easier.

Parameter	Value	Unit
side A length	38	mm
side A outer diameter	40	mm
side A thickness	5	mm
side B length	40	mm
side B outer diameter	37	mm
side B thickness	5	mm
transition length	40	mm
axis offset	0	mm
ends fillet	fillet on bo...

📦 Model #3612

1 object(s)

- format STL

Protective grid STL 3D file, center-to-center: 210x110mm, mesh: 10mm - Ø5mm

Download this rectangular protective honeycomb grid model in STL format. Mounting holes are placed at the four corners (center-to-center 210x110 mm), each with a diameter of Ø5 mm. The overall dimensions reach 220x120 mm, with very large 10 mm cell size for peak ventilation. This grid serves as both a protective guard and a ventilation panel.

Parameter	Value	Unit
length or center-to-center	210	mm
width or center-to-center	110	mm
mesh size	10	mm
dual color	no
holes	yes
hole diameter	5	mm

📦 Model #3290

3 object(s)

- format STL

Small parts organizer with 6 drawers 45×30×90 mm STL 3D file, thickness: 3 mm

Download this file of a multi-drawer box in STL format. This model includes 6 drawers, arranged in 2 rows and 3 columns. Specifically, this means 2 rows of 3 drawers. Each drawer comes with an inner space of 45 mm wide, 30 mm high, and 90 mm deep. The wall thickness is 3 mm, which makes the structure solid. The drawers come with 1 divider each, which allows up to 2 sections per drawer and up to 12 sections in total. The total size of the box come to 166.5 x 76 x 99 mm. All the objects in this model are intended to be printed without support.

Parameter	Value	Unit
number of rows	2
number of columns	3
inner drawer depth	90	mm
inner drawer width	45	mm
inner drawer height	30	mm
wall thickness	3	mm
removable divider	one divider ...

📦 Model #4144

1 object(s)

- format STL

Honeycomb grille STL 3D file, 195x80mm, mesh: 4mm

Download this 3D rectangular protective grid file in STL format. The overall size is 195x80 mm, with medium 4 mm cell size for versatile use. This grid provides both mechanical protection and airflow.

Parameter	Value	Unit
length or center-to-center	195	mm
width or center-to-center	80	mm
mesh size	4	mm
dual color	no
holes	no

📦 Model #2318

1 object(s)

- format STL

Tube adapter STL file ⌀ 158–118 mm (Length: 90 mm)

Inline fitting ⌀158 mm to ⌀118 mm in STL format. Final length of this connector is 90 mm. The thickness of the tubes is identical: 3 mm. The larger-diameter tube has a sleeve length of 30 mm, the smaller one of 30 mm as well. The ends have no fillet.

Parameter	Value	Unit
side A length	30	mm
side A outer diameter	158	mm
side A thickness	3	mm
side B length	30	mm
side B outer diameter	118	mm
side B thickness	3	mm
transition length	30	mm
axis offset	0	mm
ends fillet	no fillet

📦 Model #1676

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀125 mm to 200×60 mm, thickness 3 mm + offset

Download this 3D file in STL format of a round-to-rectangular tube adapter with an external diameter of ⌀125 mm and a rectangular section with internal dimensions 200×60 mm. The shell thickness is 3 mm and the overall length is 200 mm. The adapter has an offset of 60 mm along the Z axis. A chamfer is applied on the outside of the cylindrical end.

Parameter	Value	Unit
cylinder outer diameter	125	mm
cylinder inlet length	30	mm
rectangle internal length	200	mm
rectangle internal height	60	mm
rectangle inlet length	30	mm
offset Z	60	mm
offset Y	0	mm
total length	200	mm
thickness	3	mm
chamfer	chamfer on t...

📦 Model #3491

1 object(s)

- format STL

Protective grid STL file, center-to-center: 107x107mm, mesh: 10mm - Ø5mm

3D square protective honeycomb grid model as a STL file. Mounting holes are placed at the four corners (center-to-center 107x107 mm), each with a diameter of Ø5 mm. The overall dimensions reach 117x117 mm, with very large 10 mm cell size for maximum airflow. This grid serves as both a protective guard and a ventilation panel.

Parameter	Value	Unit
length or center-to-center	107	mm
width or center-to-center	107	mm
mesh size	10	mm
dual color	no
holes	yes
hole diameter	5	mm

📦 Model #1188

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 90–68 mm (Length: 90 mm)

Tube connector ⌀90 mm to ⌀68 mm in STL 3D format. Final length of this junction is 90 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a length of 15 mm, the smaller one of 30 mm. The two axes of the tubes are offset by 10 mm. The ends are not rounded.

Parameter	Value	Unit
side A length	15	mm
side A outer diameter	90	mm
side A thickness	2	mm
side B length	30	mm
side B outer diameter	68	mm
side B thickness	2	mm
transition length	45	mm
axis offset	10	mm
ends fillet	no fillet

📦 Model #2081

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀206 mm to 300×50 mm, thickness 3 mm

3D model in STL format of a round-to-rectangular adapter with an external diameter of ⌀206 mm and a rectangular section with internal dimensions 300×50 mm. The shell thickness is 3 mm and the overall length is 150 mm. Chamfers are present on the outside of the cylindrical end and on the inside of the rectangular end.

Parameter	Value	Unit
cylinder outer diameter	206	mm
cylinder inlet length	10	mm
rectangle internal length	300	mm
rectangle internal height	50	mm
rectangle inlet length	47	mm
offset Z	0	mm
offset Y	0	mm
total length	150	mm
thickness	3	mm
chamfer	chamfers on ...

STL: Advantages and Disadvantages for 3D Printing

The STL format is, without question, a cornerstone of 3D printing. This exchange format has established itself as the universal standard for representing 3D models ever since the early days of stereolithography. Its main strength lies in its simplicity: it describes the surface of an object using countless small triangles that form a mesh. This approach, known as tessellation, makes STL 3D files universally compatible with nearly all CAD software and slicers. If you’d like to learn more about this format, check out our article STL: What Is This 3D File Format?.

One of the major advantages of the format lies in this universality: whether you’re using a complex modeling program or a simpler design tool, you can export your 3D models in STL 3D format with near certainty that they’ll be interpreted correctly by your 3D printer. This ease of exchange has played a key role in the widespread adoption of 3D printing, allowing anyone to share and print objects without worrying about software compatibility. Once again, simplicity is its greatest strength.

However, that same simplicity also brings certain limitations. The triangle mesh, while effective for describing geometry, contains no information about colors, textures, or materials. For more advanced projects requiring these details, the STL format starts to show its weaknesses. Additionally, print quality depends directly on the fineness of the tessellation: too few triangles can lead to rough or faceted surfaces, while an overly dense mesh can make the file unnecessarily heavy.

Another notable drawback is the lack of unit management. An STL file doesn’t specify whether dimensions are in millimeters, centimeters, or inches, which can sometimes cause scaling errors when importing into a slicer. Despite these limitations, the STL format remains the go-to standard for converting your 3D models into G-code — the language your printer understands. It continues to be the preferred choice for its robustness and broad compatibility, even as newer formats like 3MF emerge for more specialized needs.

What is parametric modeling?

Parametric modeling is a fundamental approach in computer-aided design (CAD) that reshapes how 3D models are created and managed. Far from being a simple drawing technique, it represents a genuine design philosophy where objects are defined not by fixed shapes, but by variables and intelligent relationships.

This method makes it possible to modify the length, width, or diameter of a part and have the entire design adapt automatically, without the need to redraw everything. At the core of the process are parameters—numerical values (length, angle, thickness, etc.)—linked together through constraints and formulas. For instance, the diameter of a hole can be defined as half the width of a plate; if the width changes, the hole’s diameter instantly adjusts, ensuring the consistency of the design. This interdependence makes 3D models flexible and responsive to changes. One of the main advantages of parametric modeling lies in its ability to simplify customization and enable rapid iteration of designs.

Whether through modeling software such as Fusion 360 or FreeCAD, or through code-based libraries like build123d, this approach allows effortless exploration of a wide range of variations. Such flexibility is especially valuable across multiple fields—from mechanical engineering and architecture to consumer product design. It saves considerable time, reduces errors, and improves the performance of parts.

By defining design intent from the start through these parameters and constraints, the model preserves its integrity and functionality even after numerous modifications. It is a powerful way to transform an idea into a tangible object, ready to adapt to new situations.