This fast attach is all steel (not aluminum) and fits 5/8 x24 barrel threads that are usually found on AR10s, 308s, etc with 7.62 ammo. The external threads are 13/16" and fits all of our filter kits (the 5", 7" 9" and 10" kits). It assists in speed cleaning since you can screw the tube on & off quickly. It DOES NOT come with a steel crush washer (sorry). This fast attach has three large discharge ports on the main body and six micro-ports for top discharge (which compensates for muzzle rise). The coating is black oxide which helps in resisting corrosion.