The round boxes that enclose sprinkler solenoid valves often get buried in the yard over time as yard debris decays and the soil layer rises. This makes them hard to find. Once they're dug out, it's often tedious to keep them exposed, and then there is a hole in the yard, or at least a depression. This riser fits into valve boxes with 6.5" or 166mm diameter lids and extends it upward, allowing the original lid to fit on top. This can get the top of the lid just above soil level again, making it easier to keep exposed and preventing rolled ankles. This is the shortest riser available, about 1" (25mm) above the existing valve box. Thick enough to be sturdy, thin enough to flex when your valve box is a bit out of round. The locking tabs are just a bit extra to ensure it stays where you put it.