The powerup in the SNES and Super Famicom Megaman (Rockman in Japan) series of games that allows players to hold extra health in a container (Similar to healing potions in bottles in the Zelda series). In the Megaman X series, players could obtain 4 subtanks throughout the game. To fill up a subtank, the player would have to obtain full health and then collect more health powerups, each one filling the subtank more.(However, subtanks didn't hold enough health to completely fill up the health bar if Megaman had found all of the heart containers)