This assembly was originally used on a HP/Agilent interferometer assembly. It consists of 2 HP10722A plane mirror converters, a HP 10703A Linear retroreflector(corner cube prism), an HP10780 receiver and two optical assemblies (cant tell if they are mirrors or prisms inside). These were used on a GCA Model 6300C Wafer Stepper and are in excellent condition. These originally cost several thousand dollars. The entire assembly measures 8-1/4" x 8-1/4" x 3-1/2" thick. Very heavy tipping the scales at 8 pounds!