Which file should I choose?
Use 1SCC311539F0001.dxf to insert the supplied editable drawing into your layout. The ZIP contains the unmodified 1SCC311539F0001.dxf.
Use OS200D02.STP.stp (revision A) to place the original solid geometry in your 3D assembly. The ZIP contains the unmodified OS200D02.STP.stp.
