This B2-AS-II Lever-Release Clamp with 1/4"-20 Screw from Really Right Stuff is compatible with most Arca-type camera plates, lens plates, and multi-purpose rails. The jaws of the clamp open wide for plates to be top-loaded quickly and easily with no mishandling of the camera during mounting.
The locking lever-release is opened or closed by only using finger force, and once the clamp is locked down onto the plate, it has a holding power of up to 50 lb. At the top of the clamp, it features a non-threaded, counter-sunk center socket, which mounts through the top via a 1/4"-20 mounting screw. The clamp is compatible with Really Right Stuff, some Arca-Swiss, and Manfrotto ball heads.
The CNC machined 6061-T6 aluminum clamp has a type II black anodized finish. Index marks are laser-engraved on both sides of the clamp so a position can be repeated. Additionally, the stainless steel locking-lever has a low profile, and the lever hugs the side of the clamp very closely, so it is very unlikely to snag onto clothing or something else in the field. The clamp has a built-in bullseye spirit level, which keeps your camera leveled in a horizontal plane.