Originally Posted by noglider

I believe they are so called because they are about 18mm in diameter and 65mm in length. I don't know what the 0 is for.

These are lithium polymer or lithium-something cells which produce much higher voltage than traditional batteries, so they are not at all interchangeable. That's why it's smart that they are not the same dimensions. If anyone ever made a lithium-something battery in a traditional shape, bad things would happen.