The HLD-6 is an optional dust and splashproof battery holder and grip created especially for use with the Olympus E-M5.
The device can be separated into two parts -- one tailored to shooting in landscape orientation and one that's ideal for portraits.. OM System Power Battery Holder HLD-6 for E-M5 When shooting with the E-M5 and two batteries, you can choose which battery to use first; once it's drained, the camera will start using the second battery for uninterrupted shooting. The portrait unit includes a molded grip for stable shooting while the camera is in the vertical (portrait) orientation, a built-in shutter button, two built-in function buttons that can be programmed independently of the function buttons on the E-M5 body, a DC-IN jack for continuous powered shooting (requires the optional AC-3 Power Adapter), and a compartment for storing an optional additional BLN-1 lithium-ion battery.