Now you can mix and match, build and customize the way you select your bass strings. Whether it's a 4, 5, or 6 string bass, Elixir Strings has YOUR custom set of strings. How to use: 1. Select your foundation 4 STRING SET, 2. For 5 and 6 string players, select your Custom 5th String and/or 6th string. That's i. You are no longer stuck with having to play someones else's idea of string gauges.