Sport-Tek® PosiCharge® RacerMesh™ Polo. ST640. Thanks to our ultra-fine flat back RacerMesh, this polo has unparalleled breathability for superior cooling. PosiCharge technology locks in color and keeps logos crisp-making this value-priced essential a fan favorite all season long. 3.8-ounce, 100% polyester flat back mesh with PosiCharge technology. Moisture-wicking.Flat knit collar.Taped neck.3-button placket with dyed-to-match buttons.Set-in, open hem sleeves.Adult Sizes: XS-4XL.