Honestly, this is one of the best items I have bought regarding music accessories. It not only protects the drumhead, but it changes the sound that comes out of the drum in general - it adds to that all needed muting, and at the same time it gives a "punchy/clicky" nuance to the overall tone. Very, very useful.
You get a pair of those, they come in a handy wrap which you can store for when you'd need the second piece if you somehow manage to break the first one.
The glue is super strong, so definitely be careful when you have the thing in your hand and you're approaching the drum head - it will stick right away!
I am super happy with this and I can tell you that you'll be super happy with it too! For the price it's at, it's absolutely worth it!