The Plasma Beam-vulnerable variant.

Particle Wave Projectors are an attack of Metroid Prime in the game of the same name. In the third phase of the battle, Metroid Prime will sometimes summon two glowing balls of energy that home into Samus. Depending on what beam Metroid Prime is currently vulnerable to, will also affect the projectors' appearance. Samus does not have to use that weapon to destroy them (two Missiles can destroy any variety). Sometimes, the projectors will drop Energy Capsules and Missile Ammo when destroyed. If they hit Samus, she will be greatly damaged.