Ok, thanks. I didn't see that. I should have done more searching before posting the question. Cost is not really an issue if they last longer. Even though changing a bicycle tire is a simple enough matter, it becomes more of an issue if you are on a several hundred mile trip. I have always used the thorn resistant tubes, carried an extra standard tube, a patch kit, and a bottle of Slime. I have found out than in many cases, the super thin tubes many cyclists prefer for weight reduction cannot be repaired, with either a patch or sealant, because when they are punctured, they tend to rip, leaving a much larger hole than what punctured them, and sometimes several holes. The thorn resistant tubes don't tend to do that.