A large range of lithium button cells are available including rarer sizes like CR2354 with a step which is most suited for Polar heart rate monitors. If you are not sure of the size you need then please check our battery charts, or remember that the size of the battery is related to its name. For example CR2032 batteries are 20mm wide by 3.2mm deep, and CR1620 batteries are 16mm wide and 2.0mm deep. They all have a long shelf life, and quality is guaranteed.