MASTERCOOL 81490 () R134a Valve Core Remover Installer 100% U.S. designed, assembled and tested Designed for use of servicing valves in R134a systems with standard valve cores For high (16 mm) and low (13 mm) service port standard type valve Access and change valve cores while the A/C system is still filled with refrigerant Stainless steel ball valve design and patented thread remover lets the user block off the system while changing the valves cores, allowing for no refrigerant loss