The very first aluminum frames didn't have replaceable dropouts. So, you could bend them back a few times, but then the hanger would snap off and it would be off to the bike shop for a new frame. Thankfully, those days are over. Your Niner frame comes with a replaceable dropout that can be removed if it's bent and replaced with a Niner Replacement Derailleur Hanger. The Replacement Hanger bolts directly to the frame-it's easy. just make sure you choose the right one. One fits the EMD, Air 9, and Jet 9. The other fits the Sir 9 and MCR.Niner Replacement Derailleur Hangers are made of aluminum and come in black.