13 x 18 (6 mil) Reclosable Poly Bags With White Block 250/CaseThese bags have a white block to label the contents of the bag. The opening on the polybag is always on the first dimension listed (its width). Reclosable bags are measured by inside usable dimensions (without the zipper or lip included in the size). All poly bag sizes meet FDA and USDA specifications for food. Your product's contents are always visible through these clear low density polyethylene bags. The zipper type seal makes these bags reclosable