Brush Research's BUS4S12 single row knotted cup brushes are available in a 4" diameter. Knotted cup brushes are recommended for removal of burrs, weld scale and rust, edge blending, paint removal and surface prep. Made with 0.0118 stainless steel filament, the brush has a 1.250" trim length with a 5/8"-11 arbor hole for attachment to grinding tools.