Special Duration Up
From Inkipedia, the Splatoon wiki
Special Duration Up increases the duration of special weapons--the effects of Bubbler, Inkzooka, Kraken, Bomb Rush, and Echolocator all last longer. For Inkstrike and Killer Wail you're only given more time to aim the weapon, but the effect itself does not last longer. When Bubbler is extended to teammates, they also benefit from the increased duration, even if they don't have the Special Duration Up ability.
In-Depth Ability
Use
Gear
Special Duration Up is the main ability of: