This is the KEY for both the 3/4" and 1" QCV. It is a hollow 3/4" poly tube with a 25mm male thread on the top and an "Easy Lock" locking mechanism. To lock the key into position you simply lift up the yellow flip-cap on the QCV and push the key in. The Easy Lock will lock everything together and water flows. To un-lock you simply lift the lever on the side of the key, the water stops and you remove the key and close the flip-cap.