This is the Atomic Aquatics SS1 Adapter Assembly (3 sizes available) Features: Easily connect your SS1 to your inflator hose Three different sizes available The most common size adapter is the 1 inside diameter hose, found on nearly all of the BCDs used today The hose adapter assembly is used to properly attach your SS1 to your inflator hose. Once you have this piece, the SS1 can then be threaded onto the adapter. The SS1 can be removed from the BCD by simply unscrewing the adapter. This feature allows you to remove the SS1 for transport with your primary regulator or use on a second BCD. The most common size is the 1 inch diameter option. The other options include a 3/4- 13/16 as well as a 11/16- 3/4 option.