This is the Omniswivel Quick Disconnect Set Streamline & 2nd Stage (QDZM-YF-S) Description: Female QD: 3/8"-24 Male (Connects to a standard 1st Stage low pressure port) Male QD: Connects to any standard 9/16"-18 2nd stage regulator fitting. Details: Female QD has lock built into sleeve. Once connected, rotate the sleeve counter-clockwise 90deg to engage the lock. Male attaches to any 9/16"-18 male fitting or standard thread 2nd stage regulator. Solid Brass Construction Made with 02 compatible material Omniswivel Quick Disconnect Adapter Sets Locking.