Fotomate 2-way Macro Shot Focusing Focus Rail Slider for Canon Nikon Sony Olympus Pentax Camera D-SLR Positive locking knobs assure rock-steady focus. If you purchase two Piece macro sliders, they can be combined into a 4-direction macro slider. Suitable for all DSLR or DC with standard 1/4" screw hole. The 2-way macro slider has smooth rack and pinion movement to provide extremely fine focusing adjustment. It can support movement of 2 directions: forward, back.