Arrowhead PK8002 Replacement Stem for 2-Inch 450 and 480 Series FF Hydrants, 6-Inch Total Length

Good quality brass vacuum breaker (the box notes it as a "back flow preventer") to help prevent dirty water from your hose from siphoning back into your water system to your house. Say you leave your hose in the wash bucket when you're washing your car or leave it laying in a puddle of water. There's a good chance that dirty water is going to get sucked back up.But be careful with the small set screw that clamps down on the hose bibb thread. If you don't want the vacuum breaker to be stolen you screw the set screw (actually it's a small bolt) until the head shears off. Once you do that, it's on permanently and you'll have to replace the whole hose bibb if you need to replace the vacuum breaker. The brass material will last for ages; but there's a washer and internal metal spring and nylon stopper that can eventually wear down sooner, so the ability to just replace the vacuum breaker instead of the whole hose bibb is something to consider. If you want that ease of replacement, just leave the set screw off or don't over tighten.

I was searching for units for my 4 outdoor facets that would prevent back flow of water into my main water system. Knowing that brass never corrodes as others unit have done, I selected this item. They will last a life time at my home and even after I have departed. Replacement costs are nil for this item.

Spring is finally here and now I can use it. Overall it works fine. The vacuum breaks. It doesn't leak. The retaining thumb screw started to rust a couple of weeks of use.