The Spare Parts are not a bad thing to have. Add at least four Voile straps to your kit if you don't have them already. The 24" length is best. I've used them from keeping a boot tight, to making a binding work, to attaching a skin, and an ad hoc fix for a broken sternum strap on a back pack. They are just handy to have. Duct tape is another good thing. Wrap it around one of both of your ski poles.
You should also probably carry some sort of First Aid Kit.