This is the ScubaPro S-TEK Single Tank Adaptor For Scuba DivingFeatures: Made of lightweight marine-grade aluminum. Single cinch band makes for easier tank attachment. Design offers more vertical adjustability for fine-tuning tank positioning. Rubber grip pad helps keep tank securely in place. Fixed bolts allow for easy attachment and removal. Includes tank height adjustment strap with quick-release buckle. The S-Tek Single Tank Adapter is a convenient way to switch from double tank to single tank diving.