Review on Ketofa Self-Sealing R134a Can Tap Adapter, 1/2 to 1/4 SAE Can Bottle Opener, R-134A Valve Dispenser Tool for All Self-Sealing R-134a Cans by Michael Floyd

The product does not seal the hose like other devices. When the valve is turned fully ON (down), the piston pushes against the refrigerant cylinder piston and refrigerant flows. This part works. However, with the tap open (top), the valve must shut off the hose to prevent air from entering the manifold when changing the canister. Not this product.