MESH MEETS ITS MATCH. The Nike AeroBill Classic99 Hat combines stretchy, sweat-wicking fabric with ultrasoft mesh panels to help keep you comfortable throughout every round. - Nike AeroBill technology combines breathability with sweat-wicking comfort. - Soft mesh panels enhance ventilation. - Snapback closure lets you adjust the fit. - Twill fabric with spandex stretches for a comfortable fit. - Terry sweatband is soft and absorbent. - 86% POLYESTER,14% SPANDEX