Hejnar Photo 8 Inch Screw Adjusting Macro Rail with Arca-Swiss Clamp 10-Inch Hejnar Photo Arca-Swiss compatible lead screw micro focusing rail with rapid-positioning release button and modular 4-position clamp. 25mm micrometer adjusting macro rail featuring an ultra-precision Mitutoyo head with 0.001mm graduation increments and a 4-position quick release clamp.