From the Mega Man X video game series (also known as Rockman X)

They require 2 LR41 button cell batteries

Straight from the comfort of their biomes and right to your monitor

Particle storage tank type can also be reproduced

South Park Keychain School Bus Limited Edition Rascal Does Not Dream of Bunny Girl Senpai From the Mega Man XFeaturing driver Veronica Crabtree and the children of South Park Elementary, this limited edition keyring comes in the shape of the famous school bus that the main characters are often depicted waiting for. It is limited to 9,995 worldwide and is individually numbered on the reverse. Officially licensed Limited to 9,995 Size 70 x 19mm Individually numbered