The SunwayFoto XB-52DL 52mm ( 2.04" ) Superior Low-Profile Ballhead with Duo-Lever Clamp, which is original designed and to be patented, is specially offered for professional photographers and photographic enthusiasts. The screw knob side is for adjusting the width of the clamp, and the lever side is for locking the clamp. This Ballhead makes the ball Y-axis diameter 0.03 mm longer than the X-axis. The advantage of this change is that to make the operation more smoothly.