The Wimberley BS-100 Brass Reducer Bushing screws into the female threading upon the tripod collars of some larger telephoto lenses, essentially converting the hole to act like a 1/4"-20 threaded socket. Wimberley quick release plates use 1/4"-20 screws, not the larger 3/8"-16 size.
Reviewed by 1 customers
I have used this bushing many times on Giottos ballhead to reduce the 3/8" hole to accept 1/4 bolts. The flange (lip) of most 3/8" to 1/4" bushing is just too thick. This Wemberley bushing has a smaller flange and fits perfectly.