Organic Cotton Barrier Covers - you want to keep nasty dust mites off your mattress and away from your face. These uniquely designed certified organic barrier covers shield your mattress. and pillows from harmful exposure to those nasty dust mites. The organic Cotton cloth is so tightly woven that these allergens cannot penetrate it. Also, unlike synthetic covers, the cloth is breathable and soft to the touch. The slipcover style slides all the way around the bed's perimeter - like a fitted sheet. Also available in zip on style that covers the whole mattress. Plastic zipper is used as the teeth on metal or brass zippers allow too much space and will allow dust mites a doorway. 8-14". Custom sizes available.