MSR/AR owners know the importance of a clean bolt and bolt carrier group. Carbon and fouling can build-up in these areas, causing jams and malfunctions. The B.O.N.E. Tool was designed specifically to clean the bolt carrier assembly area of 7.62mm rifles. Simply insert the bolt into the U-shaped end of the tool and twist to scrape fouling. Use the bolt carrier reamer to scrape carbon from the bolt carrier.