Hearing aids use small button-style batteries. There are multiple different sizes available for this style of battery, so make sure you look at the instructions for your specific hearing aids to see which one is right for you. Some modern hearing aids will also use a built-in rechargeable battery that does not need to be changed. Instead, you simply place the hearing amplifiers into the charging case and it will be ready to go once fully charged. If you are not sure of the exact size or type of batteries that your hearing aid requires, please don't hesitate to ask a CVS pharmacist for assistance.