McFarlane Toys/Halo Helmet Wave 2
From Halopedia, the Halo wiki
McFarlane Toy's Halo Helmet Wave 2 is a series of action figure helmets based on Halo 3's multiplayer characters. They cannot be placed on the original figures, as they come on a base. All of the helmets feature Spartan helmets.
Set 3 includes three helmets: the Master Chief's helmet, Scout, and EVA. All are different colors.
Set 4 includes three different helmets: EOD, Hayabusa, and CQB.