This clamp is unique as its a G clamp styled clamp with a 3/8" threaded hole to take standard spigot. This fixture is useful as you can attach lights with spigot to the side of this clamp  , and you can attach the S-05 expand chain set with a hook for studio background support (note if you wish to use for this purpose you will need to buy 2 of these as package only includes 1).

The clamp fits most standard light stands and the auto-pole up to dia. 45mm