Our Barrel changing tool is precision fitted to facilitate the the replacement or installation of New Barrels, They are manufactured from 7075 T6511 for strength and are designed to fit the Barrel extension to provide the proper seating of the Barrel. The rear flat is designed for maximum grip when properly placed in your receiver vise , we presently manufacture units for AR-15 in 223/5.56 and for the AR-10 7.62/308 also for the Kodiak WK-180 in 223 Remington .