I wanted to change a few watch batteries, but I didn't want to waste a few weeks sending them in to be replaced under warranty.
There's a couple of tricks to unscrew a watch case - including one where you use scissors. I tried that method and failed on both my watches, so I figured I'd need a wrench.
This thing has a pretty decent set of tools, but the wrench seems to have minor issues. The third prong does not move. Maybe mine just froze in place, but it won't budge - though it looks like it ought to. My watch cases were tight, but not tight enough to need the third prong. Also, if you have one of the really big watches, you won't be able to fit your third prong on, anyway. I was able to fit the wrench on two side notches, and turn the case that way with no problems.
Not a bad set of tools. Works well for taking apart watch bracelets, if you use those.
Keep in mind, when changing the battery: it's good to replace o-rings, and make sure you apply some kind of silicon/dielectric grease to the threads and rings before screwing it back together again.