Hi guys! Just a heads up to all you who may be interested! I bought a Lan-Cay M9 bayonet for my Bushmaster upper with a 14.5" barrel and fixed Izzy suppressor. I wish to report the good news that it fits like a glove! The mounting ring fits snugly and the bayonet does not rattle. The mounting ring of the bayonet rests over the huder where the threads on the barrel would be and it look great! I will try to get a pic to post later. So if you have been unsure whether you wanted to order one or not, have no fear it fits and look great!