Envelope style cover has lapped seams and is end-opening with 6 inch flap. Length (exclusive of flaps) should equal length plus thickness of mattress; width should equal width plus thickness of mattress plus 1 inch. Comes with 3 pairs of tie tapes. Preshr Envelope style cover has lapped seams and is end-opening with 6 inch flap. Length (exclusive of flaps) should equal length plus thickness of mattress width should equal width plus thickness of mattress plus 1 inch. Comes with 3 pairs of tie tapes. Preshrunk cotton or cotton/polyester blend sheeting. Unbleached. Type III. 43-1/2 x 82-1/2 ins. Twenty (20) mattress covers per shipper. Alternative SKU: 7210008838492