The FAB Defense TAL-4 Tactical Vertical Foregrip is designed to provide improved hold on your weapon and more comfortable use of pressure activated devices with the dual sided optional slots. FeaturesQuality non-slip designDouble side pressure switch housingWater proof anti rattle storage compartment for two CR123 or AA batteriesBoth quick release mechanism and a secure bolt locking systemDesigned to fit on all 1913 Picatinny railsDurable & Lightweight fiberglass reinforced polymer constructionUser installed-no modification or gunsmith required