Nyon Bristle Brush Features Montana X-Treme Cleaning Brushes are some of the toughest nylon brushes in the industry. They are made with very stiff heavy duty bristles and a solid brass core to assure your firearms will get a superior cleaning with minimal effort on your part. Standard 8 x 32 thread. Nyon Bristle Brush Specifications .22 caliber Standard 8 x 32 thread Nylon Brass Rod