Battle.net Store Gift Card Balance

The Battle.net Store Gift Card Balance are cards that can be redeemed for $20, $50, or $100 in Blizzard Balance. The $20 cards were released on July 1, 2015 while the $50 and $100 weren't available until July 31, 2017. They are sold at retailers as physical cards and can be bought as a digital code from online retailers.

From Amazon.com
 * Battle.net registration required. Note: Battle.net Gift Cards can only be redeemed into US registered user accounts.
 * Load up your Battle.net balance, then use it on Blizzard Entertainment games, character services, in-game items, and more
 * Battle.net balance is simple and convenient to use.
 * Use Battle.net balance to buy World of Warcraft realm transfers and other paid services, as well as digital versions of Blizzard games like Diablo III and StarCraft II.
 * You can also use Battle.net balance to buy items in games like World of Warcraft and Hearthstone.