Such cameras have traditionally been designed for large, professional tripods which have a bigger than normal mounting screw (9.5mm, 3/8) attached to them. While current professional tripods and heads can offer this fitting as an option, these are very expensive and more often than not the photographer already has a tripod. This little adapter allows the larger socket (9.5mm, 3/8) to be mounted onto more traditional tripods that are available today and use the smaller (6.4mm, ) thread.
By simply screwing the adapter firmly into the tripod mounting socket on the base of the camera, the photographer can now mount it onto his existing tripod in the normal way. There is no need to buy a new tripod for that special camera, simply adapt the mount with one of these little steel rings and off you go.