A Sub Tank (サブタンク Sabu Tanku?), sometimes written as Sub-Tank, is a recovery item from the Mega Man X, Mega Man Zero, and Mega Man ZX series. They are usually found hidden throughout stages and will be added to the inventory once picked up. Unlike their counterparts from the classic Mega Man series, the Energy Tank, they are not available for immediate use, nor are they removed from the inventory when used. Once a Sub Tank has been found, picking up a health item when the character is at full health will instead fill up the Sub Tank. The amount the Sub Tank is filled is based on the type of health recovery item picked up.