This upgrade is really good for the Spike Factory because of how much damage they would do with the Tack Awesomizer Upgrade making it very useful. If Double Cash owned and turned on along with this upgrade, Road Spikes allow you to make a small profit in the early rounds, coming out to making $19 on Easy and $14 on Medium and Hard. If using the third tier Specialty Building for the Spike Factory and you place a free road spike, you make a whole $44.
25 (
6000 in Deluxe) and doubles the pierce of Tack Shooters. It also doubles the popping power of all Spike Factories, Bloonberry Bushes and Road Spikes. It is available for Bloons TD 5 Flash and Bloons TD 5 Deluxe.