I am a long-distance runner and have been running in Gel Kayano 19 and 20 for the past 3 years- huge fan of these shoes. I used to get knee pain before I discovered the Kayanos. This new 21 model fits a bit narrow and is not as comfortable as the 19/20 shoes. I have put ~20 miles on them already and it doesn't appear to be a new shoe break in issue. Disappointing.