Quad Burst

"Airburst Darts split into 4 instead of 3."

- In-game description

Quad Burst is an upgrade in the Military Monkey Knowledge tree introduced in the initial version of Bloons TD 6. When Quad Burst is activated, Monkey Subs with the Airburst Darts upgrade will have their darts split into four instead of three, regardless of the upgrades Monkey Sub has. To unlock Quad Burst, the player must have 8 Monkey Knowledge points invested into the Military Monkey Knowledge tree, and the 'Breaking Ballistic' Monkey Knowledge unlocked.

Summary
Quad Burst makes Airburst Darts perform much better with higher damage capability. Quad Burst still applies to Triple Darts, AP Darts, and Sub Commander. This makes Path 3 Sub deal higher damage and combined with the Sub Commander buff makes Subs more powerful in the mid-game and possibly late-game.

Tips

 * It is worth getting Quad Burst if the player frequently uses Path 3 Monkey Sub, as it allows the already fast attacking tower to deal more DPS to grouped and single target.
 * With Quad Burst and Admiral Brickell's Naval Tactics ability, it can allow Sub Commander or its predecessors to deal even more damage with one more dart.