9 x 12" - 4 Mil White Block Reclosable Poly Bags. These heavy-duty single track zipper seal poly bags are best used for medium to heavy weight products while keeping products clean, protected from dirt, dust and free from moisture. Bags are manufactured from 100% virgin, high clarity low density polyethylene (LDPE) film. White-on block area allows for part numbers, dates, or other important information to be written on and is easily visible. The white block eliminates the use for labels. Reclosable plastic zip lock bags are easy to seal and can be reused. Zip seal bags meet FDA and USDA requirements for contact with food products. Sizes listed are the inside usable dimensions of the bag. Select from many different reclosable poly bag sizes and mils to fit your packaging, shipping, displaying, organizing and storage needs.