The adidas Ultra Boost "Triple White" styles have gotten progressively easier to purchase. Not only has the brand continually restocked the shoes, it's also committed itself to making more and more colorways that tweak the equation ever so slighty.
It appears that it might have another one in the works with this pair, which allows for more grey on its white upper than others. The other noticeable thing that sets this one apart from the pack is the side support cage, which has an almost opaque, milky look.
Also on the way in terms of white Ultra Boosts is the mysterious white reflective pair.