Surveying Tunnel Prism consists of a 1" surveillance prism held in a waterproof aluminum housing and sturdy aluminum L bar holder. The weight of the mini prism is 0.45 lbs (0.20 kg) and the height is 3.5". The L bar is 0.38" x 3" (10 x 76mm) with a 3/8" wide screw hole and a 1/3" hex wrench for adjustment. Hope you will love it.