Features: Twice as original sliding distance・ conceptionally retractable. 8pcs Ball-bearings design・ multiple adjusting way of sliding tightness. Sliding Stopper built-in. Super smooth transporting belt and track design. 1/4" and 3/8" threads built-in the bottom for connecting with tripod. 1/4" and 3/8" screws built-in the top for connecting with ball-head. Built-in Spirit Level. High precision CNC technics.