REI Co-op Sahara Thermal Buttonup Long Sleeve Shirt Brown Green Paid Outdoor Hiking Camping. We took our beloved hiking shirt and "winterized" it to create the women's REI Co-op Sahara Thermal shirt. It uses hollow-core yarn for lightweight warmth that wicks away sweat and dries quickly. UPF rating 50. Size M, approx. measurements: Armpit to Armpit: 20.5" Length: 26" Preowned, no flaws or defects New to Poshmark? Use my code WhoaSandee when you sign up to get $10 off your first purchase. Tags: Plaid, flannel, hiking, outdoor, camping