Approved by the USPS for reading address and postage INSIDE the bag
The U.S. Post Office's equipment will not read through every poly bag, so they have determined and approved the ones that will work on their scanners. Don't take chances with your mail. Imagine your disappointment and expense when you learn that your mail was returned because it was jamming up the processing lines at the bulk mail center. These bags are guaranteed to work.
The "Width" represents the opening of the bag, while the "Length" represents the distance between the top of the bag and the bottom below the seal. Add an extra .25 to .5 inch to your length for critical dimensions to make allowance for the space required for the seal.