1/4" shank, .020" wire size, 20,000 Max RPM.Designed for use in restricted or hard to reach areasExcellent for deburring, blending and cleaning of surfacesSmall diameter brushes are especially designed for use on portable air and electric toolsApplications include deburring, blending, removal of rust, cleaning. End brushes are great for cylinder heads, pistons and valve ports, rubber and plastic flash removal, removal of rust, paint scale, tool polishing, and weld cleaning.