The innovative Manfrotto 555B leveling system for the 3021 Pro
(055 Pro) tripod allows you to quickly level your photo or video head,
independently from the tripod. 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.