Compo items are items that can be attached to Weapons. Compo items permanently attach to weapons even when moved to the inventory, as such there is no way to remove a compo item from a weapon. However, it is possible to replace the compo item with another one. Doing so will destroy the previous compo item. Compo items are dropped by enemies in the Martian Series. If a weapon that has compo items attached is sold, the player only gets gold for the weapon and nothing for the attached compo items.