Milwaukee Grinder Wire Brush 3" Knot Cup: For lighter duty surface cleaning a Crimped style Cup Brush is appropriate. Crimped wire is less rigid than knotted and can get into crevices more easily. Milwaukee offers a full range of Crimp and Knotted Wire Cup Brushes. This Crimp Wire Cup Brush is designed to be used on 4-1/2 or 5 inch Milwaukee and competitive Grinders with 5/8-11 threaded spindles. Made from carbon steel wire.