It is the front part of a ahead stem http://www.sjscycles.co.uk/easton-ea...ack-prod16269/

Cut it approxemately in half (at least if it is a looong one you wanted to replace with a shorter one). The part supposed to hold the handlebar is the part holding the chainstay on my bike. I was lucky that it was a good fit with the oval owersized (alu) chainstay but it could be possible to stuff some pieces of PVC pipe or similar in there on a slimmer chainstay. Been using it for at least three yrs.