Agree with Weylin, Fastflite is the way to go IMO. I've seen no evidence personally, that it shortens the life of a bow. I have it on the first bow I ever made almost 20 years ago. All that's ever been on there, and it's still goin' strong. Less stretch, better performance. B50 is good, and I've used it over the years as well, just a notch slower. Average shooter probably won't be able to tell much difference. But someone will chime in shortly and tell you Dacron is the only way to go in their opinion. Try them both at some point. You may find that some quality in one is preferable over the other, for you.