As you can see, it comes in two sizes for most any valve you can think of (I usually use the slimmer one) and makes removing and installing valves super simple, although there is a bit of a learning curve.

To remove the valves, all you have to do is place the sliver handle-looking part (they separate from the black part) over the valve keepers and whack it smartly with a BFG (Big Fucking Hammer) and the valve keepers come right out! That silver handle has a recessed hole in it and is pretty strongly magnetic, and the keepers are trapped inside it.

To install them, you place the keepers in the little 'well' around the valve head, stick the other end of the tool into the silver part and once again whack it smartly with a BFG; that little pointed nipple there on the black part forces the valve head down and inserts the keepers!  It takes a little practice, but once you get the hang of it you'll wonder how you ever lived without it. I can take out and install all the keepers in minutes, rather than using the regular screw-type valve compressors. Costs about $30 on Amazon.