Our handy USPS Postal Rates Reference Guide includes a postal specifications chart with sizes of mailers, a postage chart based on mail class, an envelope size guide, drop shipment discounts, postage rates and more. Whether you are a non-profit looking to see what your postage rate would be for a mailer or if you are a business looking to see how much sending a postcard presorted standard versus presorted first-class costs, we have it here!