Wimberley offers an innovative line of Arca-Swiss style quick-release plates for collared lenses that attach to the foot of your lens. For protection for your lens, Wimberley designed safety stops onto their plates at the front and back that will keep the expensive lenses from accidentally slipping out of the quick-release clamp. If you want to use only one of the stops or maybe neither, simply remove them with the hex key provided.
The P-10, P-20, and P-30 plates have anti-twist nubs at the back of the plate. These help to keep the plate from twisting if it is mounted with only one fastener. The unique dual-nub design provides better performance when butted against a curved surface. The P-40 and P-50 plates do not have anti-twist nubs because the lenses they are normally mounted to usually have more than one mounting hole.