Ronhill Base Thermal 300 Half Zip Running Top Thermal Regulite Fabric - Lightweight, breathable with premium wicking properties to keep you warm and dry. Added Stretch and Recovery - The garment is designed to fit snugly, with great flexibility. Cut and Sew Construction - Each component is designed to give you optimal movement. Quick Drying - The active fabric works to evaporate sweat away from the body, keeping you dry without losing heat. Flatlock Seams - Offers minimal irritation when running.