Whether you have chosen to purchase your hearing aid from Hearing Direct, or from any other retailer, it will require a power source in the shape of a battery to provide the necessary functionality. Hearing aid batteries are manufactured by a number of leading suppliers from Rayovac to Energizer. so performance and price vary from one brand to the next and from one type of power cell technology to the other. One feature which all hearing aid batteries have in common is a colour index. Because the various batteries look very similar, a colour index has been adopted by the various suppliers labelling each battery size with its own unique colour. Instead of remembering which battery size your hearing aid uses, it is easier to remember the right colour. Hearing Aid Batteries Colours Index: Size 10 - Yellow Size 13 - Orange Size 312 - Brown Size 675 - Blue Now you can easily order the right size next time you need some replacements without having to consult the manual. We recommend you carry at least one spare battery per hearing aid with you at all times, so you always have a working device - you never know when those low battery warning sounds will strike! You may find the Rayovac Battery Caddy helpful too.