Designed for all digital and film SLR cameras and used for macro photography, or film negatives taken; Suitible for , for , for and for macro bellows, macro shot extension tubes, or macro lenses; Smooth rack and pinion movement provides extremely fine focusing adjustments and positive locking knobs assure rock-steady focus; Focusing rails are essential accessories for macro photography, which requires precise distance modifications and a steady hand, as well as other situations where accurate camera positioning is crucial; The geared drive system can greatly enhance accuracy and speed of adjustment of the slider and the screw size is international standard: 1/4inch, fitting most tripods and copy stands. High Quality Colour:Black Material:Aluminum Alloy Package Contents: 1 x Rail Slider Plate Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.