I always carry one or two, even if I have spare spokes for myself. Yea, they have been a lifesaver at times. One thing of note is that if you can't get the tension you need with the fiberfix, simply tighten the adjacent spokes on each side. Btw, I do carry stuff for someone else in case they need it and for two very selfish reasons, if we're in a group, it gets me back on the road faster and I can use all the good karma I can get.