Attached is an STL file of a flat gasket / washer.

The model features an inner diameter of ⌀70 mm and an outer diameter of ⌀86 mm. Its total thickness is 10 mm, with chamfers of 3.9 mm applied to both the inner and outer diameters.

You can generate a new model with your own dimensions on iteration3d platform:

https://www.iteration3d.fr/en/templates/template-view.php?templateid=19

You can configure:

• inner diameter
• outer diameter
• thickness
• edge finish (none, fillet, or chamfer)
• finish position and side(s)