"I received a pair of the Nike Zoom Vaporfly 4% the day after release and tested them at my faster tempo paces at 8:11 for 4 miles on a hot day at 6,800 feet. My effort on the tempo run and comparisons to other runs on the same roads indicates that, at least for me, the claim of a potential 4 percent improvement in running economy may be in the ballpark. Three days later, and a bit tired, I raced them in a downhill 10K race in Salt Lake City at 4,800 feet. I averaged 7:07 per mile and won my 60-64 age group in almost the same time as my finish five years ago and only a minute slower than eight years before when I was in superb shape and ran two 1:35 half marathons."
http://running.competitor.com/2017/07/shoes-and-gear/mid-packer-runs-nike-fastest-race-shoe_166470