This item is an accessory. It must be rented with a non-accessory item.
The Nikon MB-D18 Multi-Power Battery Grip allows the Nikon D850 to be powered by a single (not included) Nikon EN-EL18a/b battery. This is the same battery in the D5 which should give you more than double the capacity of the standard EN-EL15a that comes with the D850. This larger battery will increase the fps of the D850 to 9 fps max. The MB-D18 also provides a comfortable vertical grip with an additional shutter release and scroll wheel for easy access to the camera functions when shooting in the vertical orientation. It is also fairly compact, with dimensions of 5.9 x 2.9 x 1.7" (15 x 75 x 45mm).
Please note that the grip may only be rented with cameras or other gear and not as the only item in your order.