MASTER CASTER COMPANY-PAD,SCRATCH GUARD,SRFCSVR. Scratch Guard Self-Adhesive Clear Surface Protectors, 3/4 Dia. Circles, 20/Pack. Keep keyboards, desk accessories and other electronic equipment from sliding, while protecting the surfaces they're on with these self-adhesive circular protectors. Excellent for use on glass, metal, plastic, ceramic, wood or the back of picture frames. Diameter: 3/4 in; Thickness: N/A; Material(s): No-Slip; Color(s): Crystal Clear.