Sinclair nylon bore brushes are manufactured significantly larger than bore diameter to fit your barrel properly and have a closed loop on the end. Many other brushes are undersized and don’t do an adequate job of scrubbing the barrel. Our nylon bore brushes have extremely stiff, heavy bristles which provide excellent scrubbing action in your rifle's bore. Ammonia and oil based cleaners will not “eat” or dissolve these bristles as they do bronze brushes. The nylon pistol brushes are about 1" shorter than the rifle brushes. Brushes except 17 caliber and 20 caliber are standard 8-32 male thread.