These dark green, extra-fine, 1/4" x 1/2", Cratex cylinders are approximately 40 grit.   Cratex is a tough, resilient, rubberized abrasive that utilizes silicon carbide as the abrasive grain in a standard bond of premium grade, oil-resistant chemical rubber. Its unique cushioned action allows the abrasive grains to cut freely, smoothly and softly without gouging or digging into the work surface. Ideal for work on jewelry, plastic parts, small castings and models.  Sold by the box (100 wheels per box). Max. operating speed: 25,000rpm.  Arbor hole: 1/16".     Made in Mexico. 

General uses: 

Light bur and surface deposit removal

Breaking edges, radiusing, deflashing and polishing molds, dies and other production tools

Removing rust, excess solder, heat marks, tool marks, scratches, and cleaning threads