Energizer 365/366 Watch Battery MiniPack of 1
The size 365 and size 366 watch batteries are identical in size and voltage. The 366 is optimised for "low drain", while the 366 is for "high drain" applications. "High drain" means the bursts of power required e.g. when you press the light button on your watch. Because the 365 does everything the 366 does, and more, Energizer has streamlined production and now only makes one battery.