Ring of Fire

"Throws out a fiery hot burst of flame that can pop anything"

- Bloons Tower Defense 4 Description

The Ring of Fire is the final upgrade for the Tack Shooter in Bloons TD 4. It is a level 4 upgrade unlocked at Rank 22. Ring of Fire is effective against all bloons, but it cannot detect camo bloons without other special towers around. Unlike firing in 8 directions like its previous upgrades, it shoots fire in a 360 degree range. This upgrade costs $2125 on Easy, $2500 on Medium and $2700 on Hard.

This tower is very useful and usually has a high pop count after waves 60+. In BTD4, this tower is a lot more effective than a Blade Shooter. This upgrade is good for thinning out several bloons packed together.

Strategy
The Ring of Fire fires at a rate slightly faster than the Tack Tower, and there are no holes in its range (sometimes, some of the bloons can slip between the tacks). If you pack many Rings of Fire together, even Ceramic Bloons can be popped in a few seconds.

Upgraded from (BTD4)
Tack Shooter→Faster Shooting→Extra Range→Blade Shooter→Ring of Fire

Bloons TD 5
The Ring of Fire is also in Bloons TD 5. It is the last upgrade for path 1. It shoots out a circle of fire that can pop Lead Bloons and Frozen Bloons and can kill up to 60 Bloons per pop. However, it cannot detect or target Camo Bloons unless there is a Radar Scanner or a Meerkat Spy. It is almost the same as it was in Bloons Tower Defense 4.

Trivia

 * The iPod touch/iPhone version of the Ring of Fire has a greatly increased firing rate but does not shoot in a ring, rather with bursts of fire in 8 different directions. However, the disadvantage to this are the "holes" between the fire bursts.
 * The advantage is that it can do extra damage to M.O.A.B. Class Bloons this way.
 * Lag can reduce the Ring of Fire's firing rate dramatically, especially when comparing it with the speed of the bloons.
 * The Ring of Fire has a slightly greater range than the Blade Shooter in BTD4.
 * The Tack Sprayer upgrade might be slightly more powerful than the Ring of Fire if Premium Upgrade Tack Awesomizer has been purchased. The Tack Sprayer is also better against MOAB-Class Bloons
 * If you have a ring of fire, the tower must touch the bloons and will not miss. In the iOS version, however, there are 8 separate flames, making missing possible.
 * This is the only upgrade for the Tack Shooter that allows it to pop Lead and Frozen Bloons.
 * In BTD5, the icon of Ring of Fire is an explosion, instead of a flame, fire or similar.
 * In the PC version of BTD4, BTD4E, and BTD5, the Ring of Fire is impossible for the bloons to dodge (literally!).
 * In BTD5 when it has increased the range by the Pontoon Pro or/and Monkey Beacon, it seems that the range will stack.