8-Inch Hejnar Photo Arca-Swiss screw adjusting macro focusing rail with 0.004 inch fine control lead screw and quick-positioning button. Hejnar Photo 10 Inch Lead Screw Micro Focusing Rail with Quick Release Clamp 25mm micrometer adjusting macro rail featuring an ultra-precision Mitutoyo head with 0.001mm graduation increments and a 4-position quick release clamp.