The Brownell loop material is 100%nylon. They make the camo which is .078 dia. soft, and the black .083 dia. rigid. I like the camo. And when you burn the ends it will ball up very quickly, and the camo one is easy to work.
Bcy release rope, I think it is 2mm dia. I heard it is excellent for making string loops but I hav'nt used it. Good Luck in your choices.