Features helm rotor supported by 3 roller bearings, ball bearing piston race, simplified integrated metal construction, field replaceable shaft seal, -5 ORB port threads, internal pressure relief valve, front of dash fill, lock valve for positive rudder lock, patented bleed tubes and internal air pocket to eliminate oil expansion overflow. Compact and stylish. Fits 3'' dash hole for round look with retro fit of 4-1/2'' dash hole for standard square look. Equipped with adjustable O-ring fittings to simplify the installation process and allow for simple reorientation of the fittings after installation. Type Dometic 1.7 Mount Rear Helms with part numbers ending in "3" are equipped with adjustable O-ring fittings allows for simple reorientation of the fittings after installation.