Recurring 'Rangs

 is an upgrade in the Primary Monkey Knowledge tree, added in Version 22.0. It allows boomerangs of Boomerang Monkeys to rotate in a second full circle before returning if they have not yet reached their pierce limit. It requires five primary knowledge points invested and Extra Bounce.

Because Recurring 'Rangs had replaced Ambidextrous 'Rangs in Version 22.0, players who had unlocked Ambidextrous 'Rangs automatically unlocked Recurring 'Rangs.

Summary
Recurring 'Rangs utilizes each boomerang to its maximum potential. It sees the best use in combination with Bionic Boomerang, Turbo Charge, and Perma Charge, because their combined high pierce and attack speed allows more boomerangs to maximize use of the double return mechanic, but this perk also comes useful for the Kylie Boomerang because its boomerangs are able to rehit bloons unlike the other three.

Tips

 * Although it does not seem useful at first, Recurring 'Rangs can help Boomerang Monkeys inflict more damage overall as long as the boomerangs don't reach their pop limit. In addition, the extra boomerangs can actually improve the overall pierce for a Boomerang Monkey, especially for really fast attacking Boomerang Monkeys like Turbo Charge or Perma Charge.
 * This MK is most useful for Bionic Boomerang and above, as their combined fast attack speed and fixed curved throwing pattern can cause many of its boomerangs to waste maximum pierce potential, especially when paired with the Glaives crosspath. Adding Recurring 'Rangs ensures the boomerangs utilize as much pierce as possible, occasionally acting as source of extra damage.
 * This MK does not affect nor benefit Glaive Ricochet and above, as the ricocheting nature of the glaives prevents them from returning to the Boomerang Monkey.
 * The effects of Recurring 'Rangs can also apply for Kylie Boomerang. This is useful, as Kylie Boomerang projectiles have considerably high pierce, and for MOAB Press for similar reasons. In fact, since their boomerangs can rehit the same bloons more than once, it will always act as extra sources of popping power.

Trivia

 * Recurring 'Rangs is based on the third upgrade of the Boomerang Dojo specialty building in BTD5.
 * In Version 24.1, there was an odd bug that occurred where Recurring 'Rangs automatically got unequipped from players. On March 18th/19th 2021, Ninja Kiwi compensated every player affected by this bug by rewarding all of them one free Monkey Knowledge Point. The message "Recurring Rangs was accidentally removed from your account. Here's your Monkey Knowledge point refund!" was accompanied for the "Gift Received" messagebox alongside the free Monkey Knowledge Point.