This Presma aluminum vertical foregrip pulls double duty: a positive forward hold plus an internal dry-storage cavity. The O-ring-sealed compartment keeps spare batteries or small parts dry, and the clamp-on base mounts to any Picatinny rail. Features: Aluminum vertical foregrip Internal O-ring-sealed dry-storage cavity Clamp-on Picatinny mount Holds batteries or small parts Mounts to any standard Picatinny rail, including AR-15 handguards and rail systems.