A steady mount that will move your optical assembly back and forth. Made with anodized aluminum, this has many interesting things to make your brain start thinking. It comes with a gear and ball bearing forward/backward motion sliding mechanism mount. There is a stop at each end of the track. The track is 12-1/4 inches long by 1-3/8 inches wide. The sliding mount is 3-3/8 inches long by 3 inches wide. Attached to the sliding mount is an optical holder assembly mount. There is a clamp that fastens with a screw to hold the optical assembly in place. There is a large plate where the image comes in and on the other side is a spring loaded blocking plate. The opening on the large plate is 2-7/8 inches by 2 inches. The spring loaded plate works by turning the white plastic screw on the side attached to a gear counter clockwise.