Spilt Flash Collar has a hidden bolt for outdoor flag pole installation which stands 2-1/2 in. tall. Spun aluminum is approximately .080 in. thick. Remember on ground installations, that the outside diameter of the collar should be at least 1 in. larger than the diameter of the foundation sleeve. The inner diameter of the collar will be approximately 1/8 in. larger than the shaft. At installation, spaces should be sealed to prevent water from entering the ground sleeve.