These honestly may be the most comfortable shoe I have ever put on and owned in my life. They are a perfect "quick" run shoe, as in my opinion 6 miles or less. After 6 miles or so my feet began to hurt bad, real bad. The first 6 miles, like riding on a cloud. I use these as my speed trainer and my other brand shoe as my longer run shoe. With all that said, I have no negative review on the shoe whatsoever as I believe they weren't necessarily intended for a real long run. If you are looking for a trainer that is comfortable, extremely light, and make you go faster than you thought possible; look nowhere else than the Cloud X. This is my first experience with the On-Cloud brand and I love them. I will be buying other platforms of the On brand as in everyday wear, that's how impressed I am.