Originally Posted by
flippinsweet
This came in the box with the new bike. What is is for?
Unknown Item
It's a replacement derailer hanger. If you crash or suck the derailer into the wheel, a replaceable hanger is weak and will break. This saves the frame and you just put the new one in place. This one is a spare and could be useful in the future. Put it someplace that you can remember where it is.