The Ruger American Rifle Generation II stock features a comb riser to adjust the height of the comb for better sight alignment. The rifle comes with the LOW comb installed, which raises the comb height by 1/2'', suitable for many shooters using mid-power magnified optics. The comb risers in this kit provide extra height to position the shooter's eye directly behind the sight. One comb in the kit increases the height by 5/8'', while the other adds 3/4''. Combs are easily swapped by loosening the recoil pad assembly and sliding the comb off. A 1/8'' hex wrench or similar tool is needed to loosen the rear swivel stud for changing the combs.