Mueller 1/2 in. MIP MHT Anti-Siphon Brass Sillcock Valve

Prevents outside faucet freezing and protects against back siphoning. A built in backflow preventer checks siphoning back into the water supply. The sillcock drains automatically upon water shut off if the hose is removed or open. 1/2 inch nominal copper sweat or 1/2 inch M.I.P.