9-Inch Nails

"Engineer's nailgun upgrades to shoot massive 9-inch nails that can pop 8 bloons at once including Frozen Bloons."

- Official BMC description

 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 acts much like a Spike-O-Pult or an Intense Magic Monkey Apprentice and therefore, this is best used on the end of a long line. This upgrade is comparable to a boosted version of the Dart Monkey path 1 upgrades. Unfortunately, it only affects the engineer's nail gun, not the sentries.

It costs $385 in Easy, $450 in Medium, $485 in Hard, and $540 in Impoppable. It also takes 700 to Research in BMC.

Strategies

 * Place it at the end of straight lines to get the full use of its popping power.

Trivia

 * The upgrade name may be a reference to the industrial rock band Nine Inch Nails.
 * This upgrade was replaced by Oversize Nails in BTD6.
 * 9-Inch Nails is the only upgrade in the Bloons TD series to start with a numerical character.
 * 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).