Here`s an easy way to add refrigeration oil to an A/C system during service--especially handy with flushing or retrofits when all oil has been removed from the system. It takes just seconds to transfer an oil charge while the system is in a vacuum. The injectors are great add-ons to recovery/recycling and charging. Installs in-line on the low side of the manifold. Made of durable polypropylene with oil levels marked in ounces and milliliters. Solid brass fitting with a Lexan(R) handwheel. R-134a Oil Injector with 1/2" Acme fit. Robinair 34065 Oil Injector For R-134a