If your talking about the image you have in your first posting it's resin filled fiberglass and either mounts in a hole in the tank turret or in the bracket commonly called a sugar scoop or one of the flimsy aluminum brackets they hung on the back of the early HMMWV. On the 151 it would mount in a sugar scoop on the antenna pylon on one of the rear corners. The image MWMULES posted is the side mount bracket for the guard receiver in a 151 but that base will only accept the AB-15 antenna base pictured. The AB-15 is a 2 piece porcelain unit that screws apart, drops through a 2" hole in the bracket and then screws back together. It used the same MS-116, 117, and 118 masts or the AT-1095. The rubber flex section is the same as the one in the AB-558.