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Bloons Wiki
Engineer's nailgun upgrades to shoot massive 9-inch nails that can pop 8 bloons at once including Frozen Bloons.
~ Official BMC description

9-inch nails (parsed 9-Inch Nails in Bloons Monkey City) is the first upgrade of the second path for the Monkey Engineer. It allows it to pop up to eight Bloons at once, including frozen bloons. It doesn’t affect Engineer’s sentries.

It costs $385 in Easy, $450 in Medium, $485 in Hard, and $540 in Impoppable. In BMC Flash, it costs $700, and it also takes 700 City Cash to Research in all version of BMC. In BTDB Mobile, it costs $450.



The 9-inch nails upgrade makes the Monkey Engineer very powerful when it comes to grouped bloons due to his ability to pop over twice as many bloons with his nails. In terms of its function, it's very similar to a Spike-O-Pult or an Intense Magic Monkey Apprentice. Sentries from the 1-0 path line are not affected, only the engineer's nail gun.


  • Place it at the end of straight lines to get the full use of its popping power.
  • Using 9-inch nails and an Ice Tower together in a curved path deals well against early grouped bloons.




  • 9-inch nails is the only upgrade in the Bloons TD series that is spelled in all lowercase in certain games. The reason for this is unknown.
    • In Bloons Monkey City Flash, it is parsed "9-Inch Nails" in the Upgrades menu in the city, but is parsed "9-inch nails" in its tooltip when attacking a tile.
    • In Bloons TD 5 and Bloons Monkey City, it is also the only upgrade to contain a numerical character within its name (upgrades such as Point Five Oh and Ground Zero do not count, because the number's name is written out).
  • The upgrade name may be a reference to the industrial rock band Nine Inch Nails.
  • This upgrade was renamed to Oversize Nails in BTD6.
  • 9-inch nails is the only upgrade in the Bloons TD series to start with a numerical character.
  • In BMC Flash, 9-Inch Nails costs $700 ingame. It doesn't cost this much anywhere else.