This 11 in. diameter Master Sweep Round Wire Brush Head by Rutland features a plated, double swaged 3/8 in. thread fitting of the traditional course NPT type thread. This brush head comes with tough, durable round wire bristles and has a heavy duty double spiral 0.177 diameter spindle design. The seven in. of fill is two on two high density, oil tempered 22 gauge wire bristles that create uniform and rugged bristle distribution. Master Sweep is the brush that cleans chimneys more thoroughly while it outlasts all other chimney cleaning brushes - making it the leader in the cleaning industry. Master Sweep round chimney brush head with an 11-inch overall diameter. Features a plated, double swaged 3/8-inch thread fitting of the traditional-course NPT-type thread. Tough, durable round wire bristles. Brush head has a has a heavy-duty double spiral 0.177 dia. spindle design. The seven inches of fill is two on two high density oil tempered 22 gauge 0.0286-inch wire bristles, creating uniform rugged bristle distribution. Master Sweep brush heads are long-lasting professional brushes that withstand the demanding abuse encountered by busy commercial chimney sweeps. Cleans chimneys more thoroughly and outlasts many comparably priced brush heads.