4 Way Macro Focusing Rail Slider for Canon EOS 450D, 1000D, 550D, 400D, 500D, 350D, Xsi, T1i, T2i, Xti, XS, XT, 50D, 40D, 10D, 20D, 7D, 5D Mark II, 1D Mark II, III, IV, 1Ds Designed for all digital and film SLR cameras Smooth rack and pinion movement provides extremely fine focusing adjustment Used for macro photography, or film negatives taken suitible for most Canon EOS, Nikon, Minolta and Pentax macro bellows, macro shot extension tubes, or macro lenses 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