Battery sizes are usually denoted by a combination of letters or numbers. As an importer, you will need to decide which size is most appropriate for your product.
Secondary cells in today’s electronic devices are often prismatic or pouch cells which can be bespoke sizes and, therefore, don’t appear in this list of standard battery sizes (although some rechargeable batteries on the market, such as NiCd AAs, for example, will adhere to these standard sizes):
Table courtesy of Battery University.