The MB-D18 battery grip is for the D850. This grip extends the battery life to well past 5100 shots. The grip allows you to shoot vertically with ease due to an added shutter button located on the grip. The D850 will shoot 7fps in burst mode out of the box, but with the added help of the grip you are now able to shoot 9fps.
MS-D12 Holder for AA Batteries available upon request