They were used on the old Military C-Rations. They are pretty Handy to Have around, Especially for Camping. They will last a lifetime and then some. They Never Need Sharpening, & Will Always Work When the Power Goes Out. One of the Ones that I use on a regular basis has been used for over 20 years, and I am able to open a can faster than the electric can opener that my Wife prefers to use. There compact size allows them to be stored almost anywhere, even on your key ring.