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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 $490 on Easy, $575 on Medium, $620 on Hard, and $690 on Impoppable.



An Engineer with Sprockets receives a black construction helmet with two green arrowhead symbols pointing downwards. On the Engineer's left hand, the wrench's grip is changed from red to yellow. On the upgrade portrait, the Engineer leans on his sentry in a casual way, leaning with his left arm, crossing his legs while standing up, and looking at the sentry while smiling.

Crosspathing with path 2 places a yellow, or white with blue lead pencil atop the Engineer's left ear.

Crosspathing with path 3 adds a grey extension to the nail gun's barrel, and paints the helmet's front white, before swapping it for a dark grey helmet and giving the Engineer a pair of orange and black gloves.


Sprockets grants 66% faster attack speed (0.6x attack cooldown) to both the Engineer's nail gun and their sentries.

When crosspathed with Pin, the sentries may also pin bloons.

Targeting Priorities[]

Sprockets targets bloons using the standard targeting priorities. Its main attack shoots straight movement projectiles.

  • First: Targets the first bloon visible within its range.
  • Last: Targets the last bloon visible within its range.
  • Close: Targets the closest bloon visible within its range.
  • Strong: Targets the strongest bloon visible within its range.

Sprockets, like all Engineers with Path 1 upgrades, can deploy sub-towers called sentries, targeting them such that they prioritize unoccupied land. Newly spawned sentries inherit the parent Engineer's targeting priorities, and also shoot straight movement projectiles. Targeting priority for all sentries use standard targeting priorities (First, Last, Close, Strong) and can be changed at any time.


Updated as of Version 31.0
Easy Medium Hard Impoppable
Upgrade Cost (3-x-x) $490 $575 $620 $690
Total Cost (3-0-0) $TBA $1,875 $2,020 $TBA
Total Cost (3-1-0) $TBA $TBA $TBA $TBA
Total Cost (3-2-0) $TBA $TBA $TBA $TBA
Total Cost (3-0-1) $TBA $TBA $TBA $TBA
Total Cost (3-0-2) $TBA $TBA $TBA $TBA

Type of Sentry[]

Sprockets Nail Sentry[]

Sprockets Nail Sentry, a Nail Sentry with higher stats

Sprockets Nail Sentry is simply an upgraded version of a Nail Sentry, and is named as a "Sentry". Just like the normal Nail Sentry, the Sprockets Nail Sentry appears green and shoots nails. It shoot nails every 0.57 seconds, and each nail can pop 2 bloons (3 with Oversize Nails) and they have a range of 45 (+4 with Larger Service Area). The nails are of the sharp damage type and cannot pop lead or frozen without special upgrades. Crosspathing with Oversize Nails changes the sentry damage type from sharp to shatter (sharp + frozen-popping). One unique crosspathing interaction is being able to receive benefits exclusive to the Pin upgrade, allowing these sentries to pin bloons.

  • Damage Type: Sharp Type (pops Black, White, Purple) Sharp
  • Damage: 1
  • Pierce: 2 (3 with 1-0-1)
  • Attack Speed: 1.75x (every 0.95s)



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.
  • Crosspathing for Sprockets mostly depends on the needs of the defense, 3-0-2 for early-game defense, and 3-2-0 for dealing more damage to MOAB-class bloons. The Pin from 3-0-2 helps the Engineer and sentries to stop bloons in place, in addition to extra pierce from Oversize Nails. On the other hand, 3-2-0 can increase the DPS versus MOAB-class bloons a little further.
  • 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:


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).
  • Sprockets requires the Sentry Gun upgrade, because said upgrade is in the path of Sprockets. In constrast in BTD5, it is possible to get Sprockets without having Sentry Guns.