The 40MM Disk Brush Wheels Two Pack brushes are specifically designed to clean 40MM weapons. They attach onto the Memory-Flex(R) rods by first attaching the 40MM Arbor on the end of the cable, and then sliding the brushes down, one at a time, until they sit tightly against the arbor. As a customer in need of our Military products, let us find the perfect cleaning system for you at specially negotiated pricing. Please contact our Military Sales Team at military@otistec.com or 1-800-OTISGUN (684-7486).