The 3N High Performance polishing rings may be attached to any handheld grinder with a 7 inch backer pad, or used on the LAVINA 7 PRO edger. The 3N High Performance 7" Polishing Rings are designed to polish edges on concrete floors after they have been grinded and honed with the 3N Copper Rings. This special bond will produce a high gloss shine on concrete. For dry applications only! With a 5" center hole and a 7" outer diameter, these edge polishing rings come in 50 grit to Buff.