The OTS Quick Disconnect (QD) Adapter Set consists of a female QD with 9/16"-18 male threads that connects to a standard regulator second-stage hose for Scuba or Full Face Mask (FFM) Second Stage Regulators and measures (L x Dia.) 1.5" x .75" (38mm x 19mm). The Male QD has 9/16"-18 female threads that connects to a standard regulator fitting or all Omni swivels. The male QD Adapter measures (L x Dia.) 1.25" x .75" (32mm x 19mm) and both components are made using solid chromed brass material that is oxygen compatible. The Female QD has lock built into sleeve. Once connected, rotate the sleeve counter-clockwise 90°-degrees to engage the lock. All OTS Swivel products are proudly made in the U.S.A.