Ultra-light, stretch-woven fabric for totally unrestricted movement. Internal mesh liner helps moisture escape & laser perforations add breathability. 4-way stretch material moves better in every direction. Material wicks sweat & dries really fast. Updated, expandable center-back pocket is water-resistant & keeps your phone secure, with no bouncing. Encased elastic waistband with internal drawcord. Reflective details for low-light runs