The Nike Mayfly is a minimalist racing shoe designed for the runner with an efficient running style looking to break their personal bests. Ripstop nylon upper with synthetic toe piece. Phylite™ midsole/outsole combination with rubber pods. This shoe is not designed to pound out the miles. It weighs just 4.8 ounces and lasts only 100 kilometers (62 miles), but that's the quickest 100 kilometers you are likely to run. Wt. 4.8 oz.