This Rutland 8 in. x 12 in. Rectangular 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 connector and comes with tough and durable round wire bristles and has a heavy duty double spiral 0.177 diameter spindle design. This brush also comes with 7 in. of fill that is two on two high density, oil tempered 22 gauge wire bristles that create uniform and rugged bristle distribution throughout the brush head. Master Sweep chimney brush head with an 8-inch x 12-inch rectangular shape. 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.