Feature: 1. Parameter Description: The total length of the slide rail is 18cm/7.1in, the effective working stroke is 16cm/6.3in, double sided calibration is clear, accurate positioning, improve work efficiency. 2. Well Designed: Double sided 38mm for Arca mount design, can be directly installed on ball head. The top quick load plate has for Arca mount design with camera strap buckle. 3. Wide Application: Equipped with 4 independent nails, detachable design, easy to disassemble and assemble, convenient to use in flat places such as desktop and floor. 4. Using Method: Rotary movement or through the foldable hand on the knob movement, rotation can be 1.25mm displacement, precise displacement. 5. Easy to Use: The base in the stable condition, large area hollow weight reduction design, double guide rail can be used superposition, in front and back at the same time can also move around, so that the photo more flexible and interesting. 6. High Compatibility: Bottom design with 3/8in screw hole, with adapter screw to convert to 1/4in screw hole, easy to install directly to most of the market tripod and head. Specification: Item Type: Macro Focusing Rail Material: Aluminum Alloy Color: As Picture Shown Application: for Digital SLR Cameras Gross Weight: Approx.578g/20.4oz Effective Stroke: 16cm/6.3in Loading Weight: 5kg/11.0lb. Package List: 1 x Macro Focusing Rail Note: Please allow 1‑3mm error due to manual measurement. Thanks for your understanding.