Engineered for high intensity year round activities, Ventilator is a unique two sided fabric with horizontal venting channels which pushes excess heat and moisture to the surface allowing for quick cooling evaporation while providing sun production. The new Ventilator fabricis the lightest and most packablefabric available,offeringbreathability, lightweight feeling, and UPF protection. From working out to climbing mountains, thisunderwear has been fabricated to not only be dependable but extremely comfortable.WARNING: Cancer and Reproductive Harm -www.P65Warnings.ca.gov