Energy Tank
Increases Samus's maximum energy by 100 units. Each tank acts as an additional health bar. Collecting these is crucial for survival against tougher Metroids.
Missile Expansion
Increases Samus's maximum missile capacity by 5. Given the reliance on missiles for Metroid battles, these are highly valuable.
Power Bomb Expansion
Increases Samus's maximum Power Bomb capacity by 1. These rare expansions are for the most powerful explosives in the game.