I put 'em on my 50# r/d longbow turkey stick (no glass) -- an osage/bamboo homemade -- and gained 2 fps. I put 'em on a 54# Lightning Longbow (glass) and lost 2 fps. Go figure. Frankly, I don't care about tiny increments in speed. I just wish they weren't so shiny, as I don't own so many bows that I have some for looks and some to hunt with. I really like these Skins and them what sells 'em, but surely wish they could develop a flat finish so that they'd not only look good, but hunt good too. Of course, I'm yet to see the real snakeskin backing that didn't shine and cost some speed. dave