They provide full waterproof protection for mattresses that are up to 18 inches deep.
Brad's Deals Editor Julie,
Use our exclusive coupon code BRADSDEALS during checkout at Linens & Hutch to get a Mattress Encasement for $26.99-$38.99. Plus shipping is free on all orders. Similar covers sell for at least $7 more at other stores. These waterproof stretchable protectors fully encase mattresses that are up to 18" deep.