There's a number of different materials you can use. I personally go with BCY Mercury and 8190F with .014 Halo for the end servings and .036 Angel Majesty for the center serving. But as far as the string materials themselves there's a plethora of various materials to choose from. This is one of the enjoyable things about being your own string maker. You get to choose what works best for you. I personally avoid anything with Vectran in it but that's just me. Some swear by it but I've never had an issue.