First-Class Forever Stamps, U.S. Flag, 20 Stamps/Book, 5 Books/PackForever stamps are always equal in value to the USPS 1 oz First Class mail price. Stamps are self stick (peel and stick) for easy mailing. USPS Forever Stamps are always valid for 1 oz First Class Mail, even when the rates go up, so stock up now before the next rate increase. Each stamp has a face value equal to the current Forever Stamp rate, so you can use multiple stamps or additional postage to cover your total shipping cost.