Precious HOCOSA of Switzerland SPORT SLEEVELESS UNDERSHIRT for Men and Women. HOCOSA Sport Woolens are made with GOTS-Certified Organic Merino Wool - available in 100% Wool or a Silk Wool blend. These certifications give you the peace-of-mind that what lies next to your skin meets the highest global standards for organic textiles. It also dictates ethical work standards and sustainable practices.