This MasterCool R-134a Valve Core Remover Installer allows the mechanic to replace a leaking or damaged valve core from a charged system with out loosing the charge or the need to recover the system down.  Ease of operation makes quick work of the removal and replacement of the core. Simply attach the tool to the low or high side fitting, depress the core tool into the core and rotate the core out, the core remains in the tool cavity while pressure pushes it outward to the top of the tool past the valve, then simply close the valve, remove the damaged core, insert a new one and reverse the process to install. It is built with a Ball valve design that controls refrigerant flow with 1/4 turn of valve lever. Lever position also gives visual indication of whether valve is opened or closed. Solid brass construction make this a durable tool for life.  Automotive R-134a Valve Core Tool remover & installer, fits HI & LO service with standard size valve cores.