Poly Seal 6×9 Blue Poly Mailers 20 Pack new 20 new Poly Seal 6×9 blue self-sealing poly mailers. These thicker mailers feature a strong adhesive seal and are perfect for shipping clothing, accessories, stickers, crafts, and other non-fragile items. New. Ships fast. #PolyMailers #PolySeal #ShippingSupplies #SmallBusiness #Packaging