Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This the the Amumu build i like to use. I've got 3 or 4 pentakills with him useing this.
Mercury Treads instead ofNinja Tabi if the enemy team has a lot CC.
Force of Nature instead ofGuardian Angel if your enemies can't kill you.
ThirdSunfire Cape, you need to switch it for thePhilosopher's Stone.