AllerZip Waterproof Bed Bug Proof Zippered Bedding Encasement, Twin XL Size (Fits 7 - 12 in. H) Cotton Protects against harmful allergens and dust mites that cause asthma, eczema, allergies Safeguards costly mattress investment Easy to fit around the mattress and box spring Easy to maintain Use with Protect-a-Bed mattress protector for optimum washing convenience