Spend the money and get concert earplugs. Not only will it save money (a basic set is only about $30), and fit better, but the event will sound better. Those foam ones are great to protect your ears, but they muffle the sound. Great if you're around power tools and the like, but terrible if you're at a concert

Concert earplugs (I have Loops, but there are countless options and each has its fans) lower the volume without significantly changing the sound. You can still hear your favorite songs, and they sound correct.