Which file should I choose?
Use NSYSFNC75_2D-front.dxf (revision V0) to insert the supplied editable drawing into your layout.
Use NSYSFNC75_3D-simplified.stp (revision V0) to place the original solid geometry in your 3D assembly. The ZIP contains the unmodified NSYSFNC75_3D-simplified.stp.
