The Entertainment Software Rating Board (ESRB) says video games offering so-called ‘loot boxes’ won’t be classified as containing gambling content.

On Wednesday, the ESRB sent an email to online “Gamer’s Guide” site Kotaku in response to a question regarding loot boxes, which offer video game players the opportunity to collect valuable in-game virtual items in exchange for real-world cash.

The contents of these loot boxes aren’t known until they’re purchased and opened, and critics have likened the process by which players open loot boxes to the anticipatory spinning of a slot machine or a roulette wheel. Calls are mounting for games featuring loot boxes to be rated ‘Adults Only,’ which would severely limit their retail distribution.

But the ESRB says it makes a distinction between ‘Real Gambling’ and ‘Simulated Gambling’, in that loot boxes always contain some form of usable content, even if some boxes contain loot that gamers would consider much more valuable and/or rare.