Martha Stewart Allergy Wise Channel Skirted Cal King Fiberbed Mattress Topper Allergy wise california king-size channel fiberbed mattress topper. 100% cotton cover with 300 thread count. Antimicrobial treated fill that inhibits the growth of bacteria on fiberfill. Skirt that is guaranteed to fit mattresses up to 20 inches deep. Hypoallergenic which reduces the likelihood of allergic reactions that may occur while sleeping.