REGULAR FIT: A slimmer athletic cut that delivers better mobility by eliminating the bulk of extra fabric. Ultra-light, smooth fabric provides extreme comfort and performance Mesh back and underarm panels provide strategic ventilation Signature Moisture Transport System - UA's signature, sweat-wicking technology pushes sweat away from your body to the surface of your gear so it dries faster. Anti-Odor - Keeps gear fresher longer by preventing the growth of odor-causing microbes. Smooth Flatlock Seams - Lie flat against your skin, eliminating rubbing and chafing to keep you comfortable and moble as you work allow a full range of motion without chafing Graphics and logos provide 360° Reflectivity - Reflector elements keep you safe and visible for training at night and in low light. Body: 3.2 oz. Polyester Mesh: 2.2 oz. Under Armour HeatGear Flyweight Run Singlet Running Vest