Rear bike wheels need careful selection, not only to ensure the hub width is suitable for your bike but also to make sure your cassette is compatible. Depending on whether you need disc brake fitting or rim brakes will narrow your selection criteria.
Rim depth is another consideration, to aero or not or if you ride off-road your selection will be based on where you ride your mountain bike. With the proliferation of disc brake-equipped bikes, bolt-thru, as opposed to quick release, becomes the standard. Choose from Bontrager, Shimano, Specialized or Zipp.