DSTE Replacement EN-EL18 EN-EL18a Battery + BL-5 Battery Chamber Cover For Nikon D800 D800E D810 D850 Camera MB-D12 MB-D18 Battery Grip Replacement battery chamber cover for the Nikon EN-EL18 EN-EL18A rechargeable battery Required when battery is teamed with MB-D12/MB-D18 battery pack Cover replaces standard tray that comes supplied with battery pack,Protects the battery chamber when using an external power supply Please note the cover is only needed when used with grip. The battery and cover kit can be used perfectly in your camera grip