【Adjustable Rail】Nitze MF15D follow focus features an adjustable rail above the 15mm rod clamp. It can be adjusted within 50 mm to fit your desired lens by twisting the red thumbscrew at the bottom. 【A/B Hard Stops】The follow focus system supports to preset A/B hard stops focal length or use 360° infinity zoom. Built-in threaded holes allow you to put A/B hard stops screws inside when not in use to prevent loss. 【Reversible Drive Gears】The follow focus kit contains 1 x 0.8 Mod/38 Teeth, 1 x 0.8 Mod/43 Teeth, 1 x 0.8 Mod/65 Teeth drive gears. And the drive gear is reversible. It can be mounted on the front or back side of the follow focus to meet different focusing needs. 【Three Marking Disks】The follow focus comes with three marking disks for interchangeble. Snap on magnetic marking disk can be easily attached or detached. 【Crank & Gear Ring Belt】T006-03 crank is included for speedy and accurate focusing. The gear ring belt can be used when your lens is without 0.8 pitch gears. 【Interchangeable Drive Gear】Nitze MF15D follow focus kit contains 1 x 0.8 Mod/38 Teeth, 1 x 0.8 Mod/43 Teeth, 1 x 0.8 Mod/65 Teeth drive gears. And the drive gear is reversible. It can be mounted on the front or back side of the follow focus to meet different focusing needs.