I have bought a couple pairs of RZEN athletic shoes, and loved them. Got me this pair because I know by experience that their shoes are very comfortable, light and made of breathable fabric. This pair is no exception, they feel great. However, the design is not at par with what I expect from such a good manufacturer. The heel is not acceptable (it poses a safety threat, if you like running in the woods like I do, a stick or anything could get caught in it). The insert slots for the shoe laces seem very weak too. I suggest that the designing team take a closer look at these details.