The HDR-300A is for King sized antenna arrays up to 25 square feet wind load area. Control cable connector, new hardened stainless steel output shaft, new North or South centered calibration. New ferrite beads on potentiometer wires to reduce RF susceptibility, new longer output shaft keyway for added reliability. heavy-duty self-centering steel mast clamp and hardware. Digital display accurate to 1 degree. Machined steel output.