This an e-mail I sent to the person in Texas whom I bought the B.M. XM15 ES2 & the Adams Arms piston kit from the internet: ******** Ijust got back from my gunsmith, he said the Adams Arms piston kit that you sold me will not work on the Bushmaster XM15 ES2 because the flash hider is welded on the 14.5" 14.5" barrel!!! Did you have any knowledge of this before you sold it to me? Kinda bummed out, I know I can sell the kit, but bummed none the less. Jim Sr. I know that being a buyer, I should have checked it B-4 buying but he included it with the rifle (saying it was for this exact rifle, I should have had him install it) I'm not a gunsmith or a black rifle specialist. I hope it will fit on the Olympic Arms AR that is due to arrive next week.