Knit 4-ways stretch. Outside 77% polyester, 23% polypropylene microfiber in contact with skin. Polypropylene: the lowest specific weight among the textile fibres. Dry fast: polypropylene is hydrophobic and keeps the moisture away from the skin, the special structure of the knit allows fast evaporation. Anti-bacterial permanent treatment: inhibits the growth of odor-causing bacteria Easy care: do not iron! Extra flat seams.