These dark-green, Coarse, 4" dia. x 1/4" thick wheels have a 1/2" arbor hole.   Maximum operating speed is 5,250rpm. Best results are usually obtained at 30% to 80% of Maximum Safe Speed. Use light work pressure.

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.  Made in Mexico. 

General uses: 

Light bur and surface deposit removal

Breaking edges, making a radius, flash removal

Removing rust, excess solder, heat marks, tool marks, scratches, cleaning threads as well as polishing molds, dies and other production tools