An item in Kantai Collection. Appears as a green bucket with "復材" (fukuzai, "recovery material") printed on it.
Its main function is to repair ships instantly. For new admirals, this equipment is rarely used or needed, but to experienced ones, it's vital equipment for ships like battleships and aircraft carriers which have ungodly long repair times that often range from hours to even days.
It is unknown exactly what's inside the bucket, though in the anime it's a magical liquid that can cause a ship girl to experience intense pleasure as a side effect of its use.
