Wheel Brush, Crosshole, 4 in Brush Dia, 1 in Face W, Crimped Filament/Wire Type, 0. They are densely filled for high aggression and long tool life and feature a 3/8 in diameter steel stem with a flat foruse in a collet or end mill holder.0118 in Filament/ Bore-Rx brushes are available in sizesranging from 3/4 to 4 in Dia and they are designed to be interpolated within bore sizes that are larger than the brush diameter.Weiler crimped wire Bore-Rx brushes are designed forautomated use in CNC machining centers and dedicated equipment.