The Mayfly is the latest Nike shoe only for racing. At 4.8 oz., it is the lightest racing shoe currently available to consumers. Nike promises 100 kilometers of wear, including a shipping label to return them for recycling when they are “finished.” How are the shoes? The midsole is comparable to other Nike racers; a molded Phylite which makes the effective range about 30-50k for the efficient and 12-15k for heavy heel strikers. The upper is ultrathin nylon – almost the thickness of a pair of nylon running shorts with just a bit of synthetic suede to hold them together. The upper graphic mimics the veins of a Mayfly, homage to the ultralight insect. If you are thinking “PR,” give the Mayfly a look.