Marmot Men's Mendocino Flannel Long Sleeve Tee 93% Hollow Core Polyester 7% Merino Wool Flannel 5.5 oz/ yd Imported Ultraviolet Protection Factor (UPF) 50 Soft, Comfortable, Mid-Weight Performance Woven Fabric with Twill Texture Technical Hollowcore Flannel for Durability and Thermal Properties Without the Weight Merino Wool for Natural Warmth Quick-Drying and Wicking