Rayovac Extra mercury free hearing aid batteries.
These batteries are colour coded as well as number coded.
Size 10 - yellow - dimensions 5.8mm diameter x 3.6mm depth
Size 312 - brown - dimensions 7.8mm diameter x 3.6mm depth
Size 13 - orange - dimensions 7.8mm diameter x 5.4mm depth
Size 675 - blue - dimensions 11.6mm diameter x 5.4mm depth
Rayovac Extra hearing aid batteries are also known as Rayovac Extra Advanced (same battery but an older version of Rayovac Extra).
Rayovac hearing aid batteries can also be supplied in other variations;
Rayovac Proline - mainly supplied by independent hearing aid audiologists - same battery, same quality but typically more expensive to buy.
Rayovac Crystal Clear - same Rayovac battery but supplied ONLY for the NHS supply chain. If you see Crystal Clear batteries for sale on eBay it is NHS property being sold, the seller is selling something that is not their property to sell. Often the top of the pack is cut off which typically states 'Made for NHS', 'Not for Resale' or similar.
Rayovac batteries typically have over 3 years of shelf life on them.