MDeVe Levelling center column 556B, Aluminum column for 3001PRO Tripods. Our innovative system means you can quickly level your photo or video head. A built-in 50mm half ball with 15° of levelling is mounted on top of the tripod center column so as to make the angle of the plate independent of the rest of the tripod. Locking and unlocking of the half ball is via a turning grip on the bottom of the center column.