9 x 24 (4 mil) Flat Poly Bags] 500/CasePoly bag opening is always on the width dimension which can be heat sealed, or closed with twist ties or bag tape 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. Our bags are manufactured from seamless poly tubing and are bottom sealed for extra strength, no side seals or slit seals.