Linear  motion micrometer screw focusing or micro  rail. The bottom rail include Arca Swiss compatible dovetail that works  with Arca Swiss type clamp while the slider is  equipped with  quick release clamp. Clamp  can be oriented in 4 positional using  center screw and dowel pins. Camera  to subject distance can be adjusted in fine increments using High-precision 100 TPI (100 turns per inch) Screw with 0-25mm range. Screws are a cost-effective alternative to micrometers where position readout is not required. Rail will work in 90 degree orientation ( perpendicular to ground) with load up to 10lb and up to 15lb in horizontal orientation (parallel to ground) . It is the best quick release system for tripods and monopods when combined with Arca style ball head and quick release clamps. International standard dove-tail rail, compatible with Arca-Swiss type quick release clamps