E. C. Moore's Plastic Garnet Snap-on Disc 3/4" Medium Grit Pkg of 200. Moore's Plastic Discs are coated with Garnet which is a naturally occurring crystalline abrasive and is dark red in color. Moore's plastic discs are flexible plastic back discs with brass centers that snap on special 3/32" mandrels, which are sold separately. Moore's discs are sold in a package of 200 individual discs. Mandrels are available in regular steel or stainless steel.