Uniqlo Boa Sweatpants, Size M, 241-400174, 09 Black The outside is a soft cotton fabric, and the inside is a boa fleece material, making it warm. It has stretch and an elastic waistband, so it's very relaxing and comfortable. The ankles are not flared, so wind is less likely to enter, providing good heat retention. There are no stains, but it has been stored, so please purchase if you don't mind.