Choose from three models - all available in three sizes: 400#, 600# and 1000# capacities.The Half-Back Gravity Flow model is the shortest of the Series. The Half-Back Gravity Flow XT is six inches taller; allowing for more antler clearance. The Half-Back Regulator lets you control how much feed is dispensed at your specified times. The dispensed feed is still maintained inside the feeder and not dumped into an open trough.