Make your house more energy efficient by insulating old doors and windows. A CMT Weatherseal bit is the perfect bit to re-groove door and window frames to accommodate wind blocking inserts. Made of solid carbide for strength and endurance. Special economical double-sided design lets you save money by offering two tips in one bit; with the same features as the one-sided weatherseal bit. Only available with a 3,5mm (9/64”) cutting diameter.