USPS - FOREVER First Class Postage Stamps (100 Stamps) 

Forever Stamps were created by the United States Postal Service® (USPS®) in 2007. They are non-denominational First Class® postage, which means that they can be used to mail First Class letters no matter what the postal rate. For example, in 2013 it cost $0.46 to mail a normal-sized letter weighing one ounce or less to an address within the United States. In 2014, the rate increased to $0.49. Customers who purchased Forever Stamps in 2013 at the rate of $0.46 each may still use those stamps to mail their First Class letters today without adding additional postage to the envelope.