10-Inch Hejnar Photo Arca-Swiss compatible lead screw micro focusing rail with rapid-positioning release button and modular 4-position clamp. 8-Inch Hejnar Photo Arca-Swiss screw adjusting macro focusing rail with 0.004 inch fine control lead screw and quick-positioning button. 50mm precision macro focusing rail with 20 TPI adjusting screw drive and indexable 4-position quick release clamp.