For some classes of service, the Post Office bases the price of the mail piece on both the weight and the shape of the item. Systems equipped with Weigh-On-The-Way® (WOW®)/Shaped Based Rating can weigh and measure the mail piece as it moves through the system when a class that requires it is selected.
Note: For a detailed description of postal services, see your Postal Authority website.
UPDATED: January 02, 2020