DSLRKIT BL-5 Battery Chamber Cap Cover for EN-EL18 Battery Grip MB-D12 NIKON D800 D800E The BL-5 is a battery chamber cover for use when powering the D800/D800E D-SLR with the MB-D12 Battery Pack and using the EN-EL18 rechargeable lithium Ion battery. Specifically designed for Nikon D800 Protects the battery chamber when using an external power supply