Flexfins 2.0 are engineered for swim training regiments and exercise routines. Designed to increase leg strength and enhance foot flexibility, our FlexFins™ 2.0 are a perfect choice for swimmers at any level that are looking to increase performance and decrease times. Color-coordinated by size for easy identification on the pool deck.Construction: 100% Natural RubberColor Coded Sizing for easy identification: XXXS (Kid's US Shoe 12-1) - Turquoise XXS (Kid's US Shoe 1-3) - Orange XS (Men's US Shoe 3-5 , Women's US 4.5-6.5) - Green S (Men's US Shoe 5-7 , Women's US 6.5-8.5) - Yellow M (Men's US Shoe 7-9 , Women's US 8.5-10.5) - Red L (Men's US Shoe 9-11 , Women's US 10.5-12.5) - White XL (Men's US Shoe 11-13 , Women's US 12.5-14.5) - Grey XXL (Men's US Shoe 13-15 , Women's US 14.5+) - Blue Please Note: If your shoe size straddles two sizes, we recommend sizing up.