Premium Hypoallergenic BED BUG Zippered Mattress Protector - Twin 100% waterproof Protects against allergens, Bed Bugs, dust mites, bacteria, perspiration Polyester surface Great for asthma, eczema and allergy sufferers Airflow Technology allows air to circulate through the protector Extra Long, 12" inch, Machine Washable, Rust proof Zipper NOTE: Outer box might say "box spring encasement" but this product is a mattress protector.