1. For macro shooting, or shooting film negatives 2. Locking knob and sliding the side knob 3. Lateral scale, moving more accurate 4. Activities Scope: 16cm 5. Bottom there is alveolar, fine sliding accurate positioning; the bottom of the standard 1 / 4 screw holes, can be directly screwed to a tripod, head to use 6. Size: 16cm x 9.5cm x 1.5cm 7. Material: Metal

http://olla.gr/2-way-macro-focus-rail-slider-long-type-tripod-head-plate-black/