ARMORED CORE WEAPON UNIT 018, Great Whistle: OIGAMI is a gigantic, articulated grenade launcher that can be attached to the weapon slots on both sides of an AC's back. This whistle measures 400mm in length, making it one of the largest weapon units in the ARMORED CORE WEAPON UNIT series.

The whistle can transition from storage mode to firing mode without the need for part replacement. Even when securely closed, it is large enough that it nearly conceals the AC.

This unit is one of the largest kits in the AC Weapon Unit series and comes packaged in a box with a lid. (This item is a reproduction.)