I did not purchase these shoes on Amazon, but from another vendor who had the 20s on clearance. I have worn the Wave Rider 19s successfully for a couple of years. The 19s are the most comfortable running shoe I have ever worn. I am a neutral runner, have narrow feet, and a low arch, and they fit great. I wore Nikes a long time but they began making them so wide they didn't fit me anymore, so a running store successfully fitted me in the Mizuno Wave Rider 19s.

Here we are in 2018 and my Wave Rider 19s have gotten some mileage on them. I saw the 20s on sale and according to various websites, the 20s are supposed to be an upgraded version of the 19s. I bought them, took them home, and ran a bit on them. They do not fit at all like the 19s. The toe box is wider and the shoe is super stiff. I really loved that the 19s were so narrow, but with the wider toe box, the 20s feel like a cross trainer, and even lacing them up as tight as I could, they still felt looser than my 19s. I personally like my athletic shoes to be super snug. And the stiffness of the shoe was just unacceptable. I ran a couple miles the first time and a couple miles the second time. The second time, I was actually feeling shin and knee pain from the shoe! I do not wear inserts; I depend on the shoe and good socks to give me my cushioning. When I put my old shoes back on, the pain went away.

I ended up returning them and buying one of the few remaining pairs of Wave Rider 19s that are still available from Amazon. This was just my experience, however. Apparently many ladies love these 20s, and everyone's feet and preferences are different. As with most other running shoes, order a half size up. If any of you really like the 19s, I suggest you buy another pair now. It is getting difficult to find them since the Wave Rider 21s have been released. Happy trails!