CottonSUPREME QUALITY & COMFORT- Our Feather Safe 4 Pack King Cotton proof pillow protector cover encasement are made with 100% breathable cotton terry that make our pillow protectors great.Our pillow covers are encasement style pillow cases . Works great with the feather pillows .WASHABLE EASY CARE: Machine Washable and tumble dry low, no ironing required. We manufactured our product with extreme care and welcome any suggesstions but if you do not like the product you can do with our hassle free return procedure.100% WATERPROOF ZIPPERED PROTECTION – Microscopic pores in the 100% Waterproof Polyurethane membrane provides protection from all other liquids to keep your pillow safe from stains. Carefully stitched with an auto locking slider does not allow accidental opening of zipper.Breathable with Cotton Rich Fabric – Our pillow encasement are made in all sizes Standard, Queen, King with a cotton rich terry cloth top to create soft, and breathable . Miracle membrane backing keeps body cool in summer and warm in winter .They come in 2 pack and 4 pack style.