The Mastercool 82934-SL Low Side Manual Safety-Lock Coupler is designed for use on all R134a systems. Its unique design allows the technician to work on the system without the worry of accidentally disconnecting the hose regardless of movement. Once the coupler is connected to the system, the safety-lock sleeve slides into place guaranteeing that the coupler cannot be taken off without unscrewing the manual valve. The 82934-SL Coupler meets all SAE, UL and EPA requirements for containment of refrigerant.