The ProMaster Dovetail Macro Sliding Rail fits ProMaster tripods, heads, and gimbals that use the Dovetail Mounting System, as well as other Arca-type products. The base of the rail attaches to a dovetail tripod head and can be slid back and forth for best positioning. 

Two dovetail clamps are connected to the base rail. The lower clamp slides along the rail to adjust the position of your camera and lens. The upper clamp acts as a quick release receiver for your camera to quickly connect to the system. The upper clamp can be mounted in one of four positions, allowing your camera or lens to be mounted in a front-to-back or side-to-side motion. 

Multiple scales are etched into the Macro Sliding Rail to aid in repeatable setups. 

This kit also includes a ProMaster 70mm Quick Release Plate (1795) which incorporate two removable safety bolts to prevent it from accidentally sliding out of the clamp. 

This system is excellent for macro photography in which small movements to the camera's distance relative to the subject can be used to change focus, composition, and reproduction ratio.