The nikon bf n2000 body cap can be placed on the camera body when no lens is attached to protect your nikon 1 camera from dust and moisture the body cap with o ring protector stored inside protects the cameras lens mount and sensor when no lens is attached the o ring protector can be taken out of the cap and used to protect the cameras o ring when shooting with a regular 1 nikkor lens rather than a 1 nikkor aw all weather lens