This is the same abrasive wheel supplied with our Manual Piston Ring End Gap Filer (Part No. 3136-101). This "late style" tool is identified by the rectangular body with a cutout at each end, and the thicker 0.15" abrasive blade.
The "early style" tool (Part No. 3131-01) had a round body and a thinner metal blade. The early style tool requires a thinner 0.08" replacement diamond-faced metal blade (Part No. 3131-DBlade).