What DCC tool are you using for your mesh creation as that changes the methods?
Or are you trying to do this in code directly in Babylon.js?
If you are just creating this in a DCC tool, general methods would be to create a cylinder at the radius that you need, delete the top/bottom and any extra faces you don’t need. Then extrude from the cylinder faces to the thickness of the rail.
If you DCC tool offers a pipe primitive, you can use that as well by slicing off faces you don’t need and then capping. Either of these methods will allow you to make both rails of the conveyor by creating the cylinders/pipes from the same origin as concentric primitives which should give you the correct inner and outer radius for the element.