Extra
Extras are a customization feature in Bloons TD 6. The menu for extras was introduced in version 10.0, though one of the extras existed beforehand under a separate menu.
List of extras
Double Cash Mode

Double Cash Mode doubles the player's starting cash and cash per pop. It can only be obtained through an in-app purchase (except in Bloons TD 6+ and Bloons TD 6 NETFLIX, where it is completely unobtainable). It is the only extra that directly affects gameplay.
Big Bloons

Big Bloons was introduced in version 10.0 and is unlocked from the Big Bloons achievement. It doubles the model size of all Bloons except Boss Bloons. Enabling this and Small Bloons at the same time causes them to cancel each other out.
Small Bloons

Small Bloons was introduced in version 12.0 and is unlocked from the Alchermistman and Bloonacleboy achievement. It halves the model size of all Bloons except Boss Bloons. Enabling this and Big Bloons at the same time causes them to cancel each other out.
Small Monkey Towers

Small Monkey Towers was introduced in version 17.0 and is unlocked from the Golden Ticket achievement. It halves the model size of all towers, without affecting projectiles. Enabling this and Big Monkey Towers at the same time causes them to cancel each other out.
Big Monkey Towers

Big Monkey Towers was introduced in version 21.0 and is unlocked from the Chunky Monkeys achievement. It doubles the model size of all towers, without affecting projectiles. Enabling this and Small Monkey Towers at the same time causes them to cancel each other out.
Small Bosses

Small Bosses was introduced in version 41.0 and is unlocked from the 25 to Life achievement. It reduces the model size of Boss Bloons to 40% of their normal size.
Gallery
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