The Infinity 556K is printed out of Haynes 282. One of the biggest selling points of the Infinity and what sets it apart from the competition is the adjustable end cap system. You can change the level of back pressure by swapping end caps and there are multiple levels of adjustment. Because of this it can perform optimally on any gun you have from a bolt action rifle all the way to a super over gassed AR or AK platform gun and anything in between. It ships in the box with the medium back pressure end cap but low back pressure and high back pressure end caps are available for purchase separately.