Highside System Injector is used for introducing any liquid into the low side of a charged hermetic system. Entirely reusable Constructed of rugged aluminum for long life Designed for use with any standard manifold gauge and requires no extra valves or fittings Drip proof, no spill design takes the mess out of maintenance The Highside System Injector helps prevent the venting of refrigerants into the atmosphere, as well as the introduction of air into an operating system. It can be used on sealed operating systems to avoid shutdowns.    INSTRUCTIONS USE WITH STANDARD MANIFOLD GAUGE. 1. Unscrew cap and fill system injector to top with liquid to be injected. Fill completely so there is no trapped air. Tighten screw top. 2. Connect the system injector as shown in the figure provided and purge the lines. 3. Slowly open valves on manifold gauge and with the high side pressure inject the liquid into the low side of the system. CAUTION ALWAYS FOLLOW THE PRODUCT MANUFACTURERS INSTRUCTIONS CONCERNING QUANTITY TO USE AND SPECIFIC PROCEDURES WHEN INJECTING LIQUIDS INTO AN OPERATING SYSTEM.  *FOR INTRODUCING ANY LIQUID INTO THE LOW SIDE OF A CHARGED HERMETIC AIR CONDITIONING OR REFRIGERATION SYSTEM 1. Maximum working pressure is 250 PSIG always connect the system injector to the low-side of an operating system. 2. Never leave the system injector connected to hoses. After use always disconnect and disassemble. 3. Before removing cap, always check for any pressure buildup, by depressing the valve core depressor. 4. Always store the system injector with the cap loose to prevent thread binding and pressure buildup. Recommended for use with Trace, Trace 2,Thawzone and Acid Neutralizer System Injector Product Sheet- PDF