By 2002, the USPS was regularly issuing self-adhesive stamps. The backing paper on these stamps often requires a larger mount compared to same size water activated stamps. Here are some of the most common sizes to fit your modern US issues. Plus Mystic makes it easy to order the correct mount size for most US stamps. Simply enter a Scott number into the search bar and click on the stamp you’d like to buy mounts for. Click the blue “Mounts” button and the correct sizes will appear!