US01. This set features 5 pieces each of the following strips (#22,24,25,27,31,36,41,44,48 and 52)needed for US single stamps. 50 pieces per pack. Showgard mounts are center split across the back for easy insertion of stamp with a crystal clear front. Mounts are gummed with an exclusive formula to insure safe, firm adhesion to the album page. They make stamp collecting more enjoyable and at the same time protect stamp values. Available only with Clear Background.