The F6402-1 V2 Lens Ring Clamp for Sigma 15mm f/2.8 Fisheye Lens from Nodal Ninja includes a plastic insert ring that mounts to the outside diameter of the lens barrel before attaching the metal lens ring. The lens ring clamp is compatible with R1, R10, R20, RS1, RS2, and M-series heads as well as other Arca-type-compatible clamps. Not only does the ring give a quick release functionality to the lens, but the by loosening the collar lock you can rotate the lens at 60 and 90° positions while mounted to any of these heads.
The lens ring clamp can be permanently left of the lens for convenience and reduces stress of the lens barrel when in use. Index markings are located on the bottom of the foot to repeat a nodal point setting on a tilt head, and the ring does not block any markings on the lens so it allows the focal distance to remain visible on the barrel. This V2 version of the ring maintains access to buttons and switches on the lens and does not block or interfere with the controls. In addition, 90° index marks on the front and 30° index marks on the back of the ring help to align the roll of the camera and lens.