When designing the sub-8 shoe, we did our research. We asked some of the world's top triathletes what they wanted in a shoe. Primarily they wanted a shoe that was fast in transition and that was easy to get on quickly. This shoe is made of 100% carbon fiber and is extremely light weight, coming in at just 225 grams, and has a super slim stack height of 3.6mm. Air is pumped into the shoe via the air gills in the arch of shoe as well as through 40 air vents.