Question: what is the difference between p312 and 312 hearing aid batteries?
Answer: 312 and P312 are the same. It is just that Power One adds an "A" in front of the battery number, but it still is a size 312 battery. ... From Wikipedia: "Zinc-air hearing aid batteries - Miniature zinc-air batteries are button cells that use oxygen in air as a reactant and have very high capacity for their size.