The adapt2 twin pack contains two 1 5/8″ x 2″ quick-release plates that each have one standard 1/4-20 camera screw and one 3/8-16 bushing. Use as additional quick-release plates for the SCA and PCA. Put one on your spotting scope, one on your camera, and one on your video camera. Then switch between them easily and quickly. >>PLEASE NOTE: THESE ACCESSORY PLATES ONLY WORK IN BOGGEAR BRAND SCA AND PCA ADAPTERS.