Fast Flite. Nothin' but. I use Dacron for tillering and long string. Others on here will swear by Dacron however. The FF is thinner, lighter, stronger and less stretch. I have heard people complain that it will damage a self bow. I've been using it for 15 years or so and have seen not the slightest bit of damage to any bow from it, ever. It can cut into the nocks on softer wood, but I add a few extra strands at the loop and the knot to fatten it up and strengthen those areas. I also have been using tip overlays which eliminate that issue altogether. Fear not, the next guy will extole the virtues of B-50. Your good either way IMO.