Throws out secondary bombs instead of frags - causing widespread explosive poppage.
Cluster Bombs is an upgrade to the Bomb Tower that made its debut in Bloons TD 5. Its first ever appearance was in the Bloons TD 5 trailer which was released on Nov 29, 2011.
It is worth nothing that this upgrade does prevent the Bomb Tower from destroying Black and Zebra Bloons without the aid of a Level 3 Bombing Range or a Monkey Intelligence Bureau. However, in BTD5, the Bomb Tower can be upgraded to Bloon Impact to be able to pop Black and Zebra Bloons without any other aid; similarly, in BTD6 this can be done by upgrading to Bomb Blitz, though that is much more expensive.
Mass amounts of these are extremely effective against non-M.O.A.B. class bloons, especially when used with the third upgrade of the Bombing Range activated.
In the Beta version of Bloons TD 5, Cluster Bombs in conjunction with Missiles would launch missiles that split into more missiles. In the release version, missiles would split into bombs.
The primary bomb with this upgrade has a slightly larger explosion radius. The secondary bombs explode with the same-sized radius as a primary bomb without this upgrade. The opposite seems to be true in the mobile versions of BTD5.
A 3-0 bomb has a maximum popping power of 360 bloons.