In Bloons TD 5, this upgrade is the 1st upgrade of path 1 for the Monkey Buccaneer, costing $340 on Easy, $400 on Medium, $430 on Hard and $480 on Impoppable. This upgrade gives the Monkey Buccaneer a pirate flag, but the flag will disappear if you purchase any tier 2 upgrade.
In BTD6, this upgrade returns as the 1st upgrade of Path 1 for the Monkey Buccaneer. It now increases the attack speed of all of the affected Monkey Buccaneer attacks (including Grape Shot and Cannon Ship, as crosspaths) by 33%. It costs $350 on Medium.