Polyester and spandex fabric blend stretches and wicks sweat to keep you comfortable when you're running hard Brief-style liner is made of recycled polyester mesh that wicks, breathes and dries fast UPF 50 sun protection Comfy waistband stays put through long training sessions; drawstring lets you adjust the fit Zippered pocket inside right hand pocket holds a key or cash Flatseam construction prevents chafing REI is Climate Neutral Certified; as we work to actively reduce our footprint, we measure annual carbon emissions and purchase an equivalent amount of verified carbon credits Contains materials that meet the bluesign® criteria