I bought one of those cheap crossbows on eBay, but after the 3rd shot the little plastic caps that hold the string on broke (exploded). After printing a new set of caps and installing them everything seemed to work out great. I am not sure about the durability of these parts, but so far so good. I printed these caps on a Replicator 2x using black ABS. Caps were sliced at .2 mm and printed with 15% infill. I only tried the caps that were printed upright. I noted that the ones printed laying on their back had less plastic in them (due to the infill), but they printed a lot faster and looked better. This object would probably be a good candidate for printing with some Nylon 618 or some other high strength material. Maybe if these ABS ones don't last i will try that.