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Increases sentry gun and Engineer attack speed.
~ Official Bloons TD 6 description.

Sprockets is the third upgrade of path 1 for the Engineer Monkey in Bloons TD 6. It allows the Engineer's nailgun and any newly spawned sentries to attack 66% faster. The Engineer's improved sentries are still deployed every 6.0s. In addition, sentries with this upgrade inherit the pinning properties of Pin.

It costs $TBA on Easy, $575 on Medium, $TBA on Hard, and $690 on Impoppable.



Sprockets primarily focuses on improving firepower via Engineer sentries. This makes the Sprockets Engineer a decent early-game advancement option in the game. Combining the Engineer's own range with his sentries, the Sprockets Engineer has rather good overall combined range and DPS for its price.


  • Adding Sprockets can allow the whole Engineer and his sentries to easily solo versus rounds with lots of Yellows and/or Pinks, where normally other sentry-based Engineers would struggle.
  • Generally, the 3-0-2 crosspath is better than the 3-2-0 crosspath. The Pin helps the Engineer, while the Oversize Nails increases pierce. Plus, sentries can now pin bloons starting from 3-0-2.
  • Sprockets tends to have better single-target popping power compared to its next upgrade Sentry Expert. However, with less pierce overall and limited utility it would help to add Gwendolin to boost pierce if opting for Sprockets spam.

Version History[]

Most problems with Sprockets were addressed with its earlier upgrades, thereby buffing the value of Sprockets in return.

12.0 (Engineer update)
  • Nerf Pierce of Sentry Gun decreased (2 → 1).
  • Buff Standard Sentry pierce increased from 1 to 2.
[...] Additionally higher tier sentries will now be able to benefit from the xx2 Pin crosspath, so enjoy some laser pins. [...]
~ Ninja Kiwi
  • Buff 3-0-2 Sentries & Higher will now also be able to Pin Bloons they pop
[...] Engineer's bottom 2 paths have a heavier support focus, so to start them off a bit easier we have shifted some starting cost out and into the non-supportive path.
~ Ninja Kiwi, referring to focus on Path 3 price buffs
  • Nerf Sprockets costs more ($525 --> $575)
    • Change Overall $0 difference in cost when taking into account 0-0-0's -$50 difference.


When a sentry is placed:

  • [gadget placement]
  • [gadget placement]


Official artwork[]


  • In BTD6, a 3-0-0 Sprockets costs exactly $2020 on Hard Difficulty. This is still the case after the Version 29.0 price adjustment of Sprockets and base Engineer.
  • Sprockets is the first upgrade to have an Impoppable price of a number whose coefficient in scientific notation is equal to 6.9 (and hence upgrades with $690, for instance).