The hybrid head series for HMS flex-shaft concrete vibrators combines round-head and square-head technology, which Wacker claims will move as much as 25 percent more concrete for better consolidation and high-speed liquification. The series includes the H 25HA (1-inch diameter), H 35HA (1 3/8-inch diameter), H 45HA (1 ¾-inch diameter, and the H 50HA (2-inch diameter), which replaces the H 55. An extended transition from square to round allows for easy removal of the vibrator head from narrowly placed reinforcement rods.