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Oval duct transition fitting STL 3D file 80x30 mm to 50x15 mm – transition: 40 mm

Enclosure with screw-mounted lid STL file: 90×50×40 mm (with ventilation on the lid)

Hose-shaped reducer STL 3D file 90.1x90 mm to 100x40 mm – transition: 100 mm

L-bracket 200×200 mm STL file, thickness 5 mm, hole diameter 6 mm

Enclosure with screw-mounted lid STL 3D file: 80×50×35 mm (with ventilation on the lid)

Small parts organizer with 25 drawers 40×30×50 mm STL 3D file, thickness: 2 mm

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

Distribution manifold 3 ways STL file – Outer diameter 50 mm, wall thickness 10 mm

Tube adapter STL file ⌀ 100–60 mm (Length: 70 mm)

Multi-compartment box STL 3D file: 14 compartments of 14×14×5 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

Rectangular box with lid STL 3D file – 78×63×20 mm, wall thickness 3 mm 📦 #6400

2 object(s) - format STL

View of object #0

Latest user-generated 3D models

Rectangular box with lid STL file – 156×66×156 mm, wall thickness 3 mm 📦 #12941

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 #2112

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀126 mm to 145.0×69.5 mm, thickness 2 mm + offset

Model in STL format of a round-to-rectangular tube adapter with an external diameter of ⌀126 mm and a rectangular section with inner dimensions 145.0×69.5 mm. The shell thickness is 2 mm and the overall length is 60 mm. The adapter has an offset of 17.5 mm along the Z axis.

Parameter	Value	Unit
cylinder outer diameter	126	mm
cylinder inlet length	15	mm
rectangle internal length	145.0	mm
rectangle internal height	69.5	mm
rectangle inlet length	10	mm
offset Z	17.5	mm
offset Y	0	mm
total length	60	mm
thickness	2	mm
chamfer	no chamfer

📦 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 #3012

1 object(s)

- format STL

Washer / Flat Gasket STL file ⌀ID: 100 mm ⌀OD: 112 mm thickness: 16 mm + fillet

File of washer / gasket in STL file format. This part features an internal diameter of ⌀100 mm and an external diameter of ⌀112 mm. The part thickness is 16 mm. A fillet is applied on the internal diameter with a value of 0.1 mm.

Parameter	Value	Unit
inner diameter	100	mm
outer diameter	112	mm
thickness	16	mm
finish	fillet
finish position	inner
sides	one side
finish value	0.1	mm

📦 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 #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 #3825

1 object(s)

- format STL

Tubing adapter STL file ⌀ 125–105 mm (Length: 110 mm)

Inline tube junction ⌀125 mm to ⌀105 mm in STL 3D format. Total length of this coupler is 110 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a length of 30 mm, the smaller one of 30 mm as well. The ends have a fillet to ease the connection.

Parameter	Value	Unit
side A length	30	mm
side A outer diameter	125	mm
side A thickness	2	mm
side B length	30	mm
side B outer diameter	105	mm
side B thickness	2	mm
transition length	50	mm
axis offset	0	mm
ends fillet	fillet on bo...

📦 Model #3273

1 object(s)

- format STL

Tubing elbow STL file 45° ⌀OD: 76 mm ⌀ID: 70 mm thickness: 3 mm

Model of an elbow with a 45° angle in STL format. This pipe elbow features an external diameter of 76 mm and an internal diameter of 70 mm. The tube thickness is therefore 3 mm.

Parameter	Value	Unit
outer diameter	76	mm
inner diameter	70	mm
angle	45	°
end fillets	no

📦 Model #2404

1 object(s)

- format STL

Tube adapter STL 3D file ⌀ 60–15 mm (Length: 105 mm)

Tube coupler ⌀60 mm to ⌀15 mm in STL format. Length of this adapter is 105 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a sleeve length of 25 mm, the smaller one of 30 mm. The axes of the tubes are off-center by 20 mm. The ends have a fillet on the outside to make tube connection easier.

Parameter	Value	Unit
side A length	25	mm
side A outer diameter	60	mm
side A thickness	2	mm
side B length	30	mm
side B outer diameter	15	mm
side B thickness	2	mm
transition length	50	mm
axis offset	20	mm
ends fillet	fillet on th...

📦 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 #3399

1 object(s)

- format STL

Tube adapter STL file ⌀ 26–10 mm (Length: 45 mm)

Straight tubing adapter ⌀26 mm to ⌀10 mm in STL format. Length of this reducer is 45 mm. The larger-diameter tube has a thickness of 2.4 mm and a sleeve length of 20 mm. The smaller-diameter tube has a thickness of 2 mm and a length of 10 mm. The ends feature an external fillet to make tube connection easier.

Parameter	Value	Unit
side A length	20	mm
side A outer diameter	26	mm
side A thickness	2.4	mm
side B length	10	mm
side B outer diameter	10	mm
side B thickness	2	mm
transition length	15	mm
axis offset	0	mm
ends fillet	fillet on th...

📦 Model #2036

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL file ⌀102 mm to 290×80 mm, thickness 3 mm

3D file in STL format of a round-to-rectangular adapter with an outer diameter of ⌀102 mm and a rectangular section with inner dimensions 290×80 mm. The wall thickness is 3 mm and the overall length is 160 mm. A chamfer is present on the outside of the cylindrical end.

Parameter	Value	Unit
cylinder outer diameter	102	mm
cylinder inlet length	70	mm
rectangle internal length	290	mm
rectangle internal height	80	mm
rectangle inlet length	30	mm
offset Z	0	mm
offset Y	0	mm
total length	160	mm
thickness	3	mm
chamfer	chamfer on t...

📦 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 #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 #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 #3317

1 object(s)

- format STL

O-ring STL file ID 17.8 × CS 1.8 mm

3D file in STL format of sealing ring with Inner diameter (ID) 17.8 mm × CS (cross section) 1.8 mm. Final diameter resulting is therefore 21.4 mm.

Parameter	Value	Unit
inner diameter (ID)	17.8	mm
cross section (CS)	1.8	mm

📦 Model #3750

1 object(s)

- format STL

Tube elbow STL 3D file 110° ⌀OD: 60 mm ⌀ID: 54 mm thickness: 3 mm

3D model of a tubing elbow with a 110° angle in STL format. This elbow features an outer diameter of 60 mm and an inner diameter of 54 mm. The tube thickness is therefore 3 mm. End fillets make it easier to assemble.

Parameter	Value	Unit
outer diameter	60	mm
inner diameter	54	mm
angle	110	°
end fillets	yes

📦 Model #1683

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL file ⌀280 mm to 100×100 mm, thickness 3 mm

Download this 3D file in STL format of a round-to-rectangular adapter with an outer diameter of ⌀280 mm and a rectangular section with inner dimensions 100×100 mm. The shell thickness is 3 mm and the total length is 200 mm. Chamfers are present on the outside of the cylindrical end and on the inside of the rectangular end to ease insertion.

Parameter	Value	Unit
cylinder outer diameter	280	mm
cylinder inlet length	25	mm
rectangle internal length	100	mm
rectangle internal height	100	mm
rectangle inlet length	50	mm
offset Z	0	mm
offset Y	0	mm
total length	200	mm
thickness	3	mm
chamfer	chamfers on ...

📦 Model #4418

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL 3D file ⌀100 mm to 200×30 mm, thickness 2 mm + offset

3D file in STL format of a round-to-rectangular adapter with an external diameter of ⌀100 mm and a rectangular section with internal dimensions 200×30 mm. The shell thickness is 2 mm and the total length is 80 mm. The adapter has an offset of 15 mm along the Y axis and 15 mm along the Z axis. Chamfers are present on the outside of the cylindrical end and on the inside of the rectangular end.

Parameter	Value	Unit
cylinder outer diameter	100	mm
cylinder inlet length	30	mm
rectangle internal length	200	mm
rectangle internal height	30	mm
rectangle inlet length	20	mm
offset Z	15	mm
offset Y	15	mm
total length	80	mm
thickness	2	mm
chamfer	chamfers on ...

📦 Model #2196

1 object(s)

- format STL

Tube adapter STL file ⌀ 26–7 mm (Length: 39 mm)

Tube adapter ⌀26 mm to ⌀7 mm in STL format. Total length of this junction is 39 mm. The thickness of the tubes is identical: 2 mm. The larger-diameter tube has a sleeve length of 15 mm, the smaller one of 14 mm. The ends are raw.

Parameter	Value	Unit
side A length	15	mm
side A outer diameter	26	mm
side A thickness	2	mm
side B length	14	mm
side B outer diameter	7	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 #2999

1 object(s)

- format STL

Round-to-Rectangular Tube Adapter STL file ⌀20 mm to 26×10 mm, thickness 2 mm

Download this model in STL format of a round-to-rectangular tube adapter with an outer diameter of ⌀20 mm and a rectangular section with inner dimensions 26×10 mm. The wall thickness is 2 mm and the total length is 50 mm.

Parameter	Value	Unit
cylinder outer diameter	20	mm
cylinder inlet length	10	mm
rectangle internal length	26	mm
rectangle internal height	10	mm
rectangle inlet length	5	mm
offset Z	0	mm
offset Y	0	mm
total length	50	mm
thickness	2	mm
chamfer	no chamfer

📦 Model #4065

3 object(s)

- format STL

Small parts organizer with 1 drawer 150×30×110 mm STL file, thickness: 4 mm

3D file of a sorting cabinet with drawers in STL format. This model features 1 compartment, arranged in 1 rows and 1 columns. Practically speaking, this means 1 rows of 1 compartments. Each compartment has usable dimensions of 150 mm wide, 30 mm high, and 110 mm deep. The wall thickness is 4 mm, which makes the structure very sturdy. The compartment features 1 divider, allowing up to 2 sections. The overall dimensions of the box are 166.5 x 42.5 x 122 mm. All the objects in this model were designed to be printed without support.

Parameter	Value	Unit
number of rows	1
number of columns	1
inner drawer depth	110	mm
inner drawer width	150	mm
inner drawer height	30	mm
wall thickness	4	mm
removable divider	one divider ...

📦 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 #3968

2 object(s)

- format STL

Enclosure with screw-mounted lid STL file: 86×40×36 mm (with ventilation on the lid and under the enclosure)

Download this enclosure model with screwed lid in STL format. The dimensions are 86 mm long by 40 mm wide and 36 mm high. The lid is 10 mm high. Side thickness is 3 mm. This enclosure has cooling area on the lid and under the base.

Parameter	Value	Unit
length	86	mm
width	40	mm
total height	36	mm
lid height	10	mm
wall thickness	3	mm
screw margin	0.2	mm
fit clearance	0.2	mm
cooling level	3
cooling zone(s)	cutouts on b...

📦 Model #2044

2 object(s)

- format STL

Small parts organizer with 20 drawers 52×40×100 mm STL file, thickness: 3 mm

3D file of a drawer organizer in 3D STL format. This model includes 20 drawers, arranged in 5 rows and 4 columns. Specifically, this means 5 rows of 4 drawers. Each drawer comes with an inner space of 52 mm wide, 40 mm high, and 100 mm deep. The wall thickness is 3 mm, which makes the structure solid. The total size of the structure are 249 x 235.5 x 109 mm. All the objects in this model are intended to be printed without support generation.

Parameter	Value	Unit
number of rows	5
number of columns	4
inner drawer depth	100	mm
inner drawer width	52	mm
inner drawer height	40	mm
wall thickness	3	mm
removable divider	none

📦 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 #5925

2 object(s)

- format STL

Rectangular-base box with lid STL 3D file – 100×50×50 mm, wall thickness 3 mm

Rectangular-base box with a lid available as a STL 3D file. Box size: 100 mm × 50 mm × 50 mm (L × W × H). Wall thickness is 3 mm. Interior and exterior edges are rounded. A small clearance is included to ensure a precise fit between the box and the lid. The inner dimensions excluding rounding are 94 mm × 44 mm × 44 mm.

Parameter	Value	Unit
length	100	mm
width	50	mm
height	50	mm
wall thikness	3	mm

📦 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 #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 #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

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.