Pferd Cup Brush, External Thread, 4 in Brush dia, 5/8-11 Arbor Hole Size, Crimped Filament/Wire Type, 0.02 in Filament/Wire dia, Carbon Steel Fill, 1-1/4 in Trim Length, 9000 RPM Maximum. Pferd 82511 External Thread Cup Brush, 4 in dia Brush, 5/8-11 Arbor Hole, 0.02 in dia Filament/Wire, Crimped, Carbon Steel Fill