According to Nike, the Alphafly line began with a prototype Air Zoom Alphafly NEXT%, worn by Eliud Kipchoge in 2019 when he covered the marathon distance in 1:59:40. Four colours make up the Nike Alphafly 4 'Sea Glass': its namesake shade plus Laser Crimson, Phantom and Burgundy Ash. Nike's spec sheet lists a carbon-fibre Flyplate, ZoomX LT foam and Air Zoom units. The upper is made from Atomknit.