Which file should I choose?
Use Sprecher-Schuh-D7Q01-Screwless-Contact-Block-STP-3D-CAD-Block.stp to place the original solid geometry in your 3D assembly. The ZIP contains the unmodified Sprecher-Schuh-D7Q01-Screwless-Contact-Block-STP-3D-CAD-Block.stp.
