I will post a photo tonight. I thought it may be a cable guide of some sort, but I now don't think that it is. The bike has cantilever brakes and the rear brakes were fully assembled, they only needed to be adjusted. Derailluer cables were also pre-installed. The only cable I had to run was to the front brakes, but I could see nowhere for this piece to go. It is tapered on one end and asymmetric, suggesting it is designed to be inserted into something. It will be much easier to describe with a picture....I will post back this evening.