Gibraltar SC-4425D-1 Cowbell / Tom Arm 9.5Mm SC-4425D 1 Tom Arm The Gibraltar tom drum arm is crafted with a 7/8" diameter post topped with a 5/16" (9 5 mm) L-rod for mounting cowbells and other percussion implements The arm's L-rod also fits some tom mounts and electronic drums The Gibraltar tom drum arm is crafted with a 7/8" diameter post topped with a 5/16" (9