Custom printed Mailing Envelopes for a professional look to any envelope. Great for Companies of all sizes, schools, colleges and personal use. All the information on the envelope can be customized to fit the feel of your company or taste. Security envelope size 4 1/2" X 9 1/2", United States First Class Postage Paid. Just include information you would like to see on your return address in the "Additional Information" at check out. For more information or to talk directly contact us by email or phone.