You can use the following letters: C, H, K, L, M, N, P, R, T, V, W & X. Numbers consist of 3, 4, 7. You can use from 2-3 letters in each code but make sure not to stack 3 letters together e.g. PRX because that will barely work. Please don't redeem 100s of codes on your account cus that's just a tad selfish, enjoy I guess:---))) ENJOY!!! ;) Enter at quest.redbull.com Each code has 8 digits 6 numbers-3,4,7 2 letters-listed above