At first glance you might think the photograph, above, is upside down; but this is a likely orientation for this adaptor.
The Inon Z Adaptor MV 1/4-20 is a quick, simple, and elegant way to attach a standard 1 inch ball adaptor to a housing or tripod that uses standard 1/4-20 tripod screws.
Most housings and many trays include 1/4-20 thread for mounting on a tripod. Now you can use that threaded hole to attach a 1 inch ball adaptor.
Applications include creating an 'upside down' tripod for underwater macro work. Attach this adaptor to the bottom of your tripod column (if it has a 1/4-20 thread) and then use a standard 1" clamp to connect a 1" ball on the top of your housing to this adaptor on that you mounted on your tripod.
Or mount this adaptor to the bottom of your underwater housing, and then mount the housing on top of your tripod or another underwater housing.