HAT SIZING TAPE: Foam hat tape with self-adhesive back to shrink hat size, can be used for fedoras, baseball cap, cowboy, western, panama hats or any other headwear with a sweatband. INSTALLATION DIRECTIONS: Cut a strip about 4-8” and place underneath sweatband inside your hat, you may need to place on either side or front and back ends of the hat depending on the shape of your hat and desired fit.
eBay