The Ruger American Rifle Generation II stock features a comb riser to adjust the height of the comb for improved sight alignment. The rifle ships with the LOW comb installed which adds 1/2" to the comb height, appropriate for many shooters using mid-power magnified optics. The comb risers in this kit provide additional comb height to present the shooter's eye directly behind the sight. One comb in the kit adds 5/8" to the comb height; the other adds 3/4" to the comb height. Combs are easily changed by loosening the recoil pad assembly and sliding the comb off. A 1/8'' hex wrench or similar tool is required to loosen the rear swivel stud to change combs.