Really Right Stuff B2-Pro-II 60mm Screw-Knob Pro Clamp

The B2-Pro-II 60mm Screw-Knob Pro Clamp by Really Right Stuff is compatible with most Arca-Swiss style camera plates, camera bars, and multi-purpose rails. It features a captive knurled knob for a better grip when applying clamping pressure, plus safety stop relief grooves to prevent plates with safety stops from accidentally slipping out when loosened. The integrated bubble level ensures precise horizontal orientation. The base features a rosette design for secure mounting to compatible ball head and other device, and will prevent twisting at the coupling point between the clamp and head over time. A legacy tongue-and-groove adapter is available separately. The top of the clamp features three threaded counter-sunk sockets, which accept 1/4"-20 and metric 6 (M6) threaded screws for mounting to a ball head stem. The outer sockets are spaced 30mm apart. The center 1/4"-20 socket is also threaded 3/8"-16 on the bottom to allow it to mount from beneath to a 3/8"-16 male stem.