- For the BTD6 counterpart, see Bigger Stacks (BTD6).
Bigger Stacks is the second upgrade in Bloons TD 4 and the first upgrade in the Path 1 in Bloons TD 5 for the Spike Factory. It allows the Spike Factory to create double sized spike piles, each pile being able to pop 10 bloons instead of 5 per pile.
- With Tack Awesomizer activated, the piles of spikes the factory produces will have 20 spikes in it.
- Following a Version 22.0 nerf for Bigger Stacks in BTD6, the cost of Bigger Stacks has always increased by $100 with each generation of BTD games.