Review on DASBET A/C Oil and Dye Injector with Quick Coupler, 2 OZ Hand-Turn Screw-in AC Coolant Filling Tube Injection Tool, 1/4 inch SAE Connector for R410A, R134A, R22, and R12 by Jerry Leon

Works great, of course used to add oil or dye to an air conditioning system. This device is intended for use in an empty, non-primed system. Fill it with suitable oil, evacuate the system and then charge it with refrigerant. Very easy to use, add oil and rotate the canister and it will push oil into the bottom of the AC line, if you set an adapter/distributor on the high pressure side, you can't siphon much oil in the previous siphoning of the system refill.