XDEEP Cargo Pouch

A thigh pouch for the kit you need to carry but don't want clipped off and swinging. Standard is fixed-volume and stays flat against the leg when it's empty. Expandable takes a folded SMB, a spool, a backup mask and gloves, then collapses back down when it isn't full.

Both mount on standard 50 mm webbing and drain through mesh panels in the base. The expandable version is the one sidemount divers tend to end up with, since there's nowhere else on that rig to put anything.