Massive nails pop 8 bloons at once, and pop Frozen Bloons.
~ BTD6 description
Oversize Nails is the 1st upgrade of Path 3 for the Engineer Monkey in BTD6. It increases the pierce of the main Engineer's nailgun nails from 3 to 8, and allows them to pop Frozen Bloons. It costs $TBA on Easy, $450 on Medium, $485 on Hard, and $540 on Impoppable.
It is not known why "Oversized Nails" no longer used the name "9-Inch Nails", but the name was likely modified to avoid confusion between real-world distance units and in-game distance units, as well as the fact that it seemed a little awkward to add a band reference for an engineer.