Forever Stamps are perfect for mailing one-ounce, standard-sized letters inside the United States. If you fear your letter may weigh more than one ounce, weigh it before applying a Forever Stamp, as larger letters will be returned owing to insufficient postage. Letters over a certain size must be sent via first class mail. Standard-sized letters up to 1 oz in weight and a maximum of 7 1/4 x 10 inches in size can be mailed at a cost of $1.20 with a single Forever Stamp. Large envelopes ($3 or more) and oversized letters ($5 or more) are also available at some post offices and shipping stores. These items are priced higher because they include additional postage per item. The Postal Service recommends that you use solid color paper when sending letters with stamps because colored ink costs more to process. However, white paper can be used instead if desired. Simply use cold water to wash off any residual color from your paper towel. Stamps should be placed on the back of the envelope so they will not get bent out of shape during handling. Stamps can be purchased at most post offices, but you may want to visit a post office before you leave home just to make sure there are no delays in the delivery of your letter.