The first polyester fibers were produced by reacting ethylene glycol and either terephthalic acid or one of its esters to give poly(ethylene terephthalate). This polymer is still used to make thin films (Mylar) and textile fibers (Dacron and Fortrel).
This stamp also may be used for mailing items weighing up to 2-ounces. These Forever stamps will always be equal in value to the applicable price for the price category printed on them, at the time of use. The initial price and value for this stamp is 71 cents, effective May 31.
Credit: Jerry Kobalenko All Canada Photos Getty Images. Each postage stamp is worth 49 cents as of 2014. Therefore, it takes three of them to cover the cost of $1.15. However, that is more postage than is needed to mail the letter, as the three stamps are equal to $1.47.