Turn a paperback into a hardcover bk in seconds with our extra-thick, 2-piece, 15-mil polyester covers. The flexible, 2-mil spine strip protects without extra weight so bks will not fan open. The covers are crystal clear with a non-yellowing cover and adhesive. They are fully adjustable to fit thin or thick paperbacks and feature an acid-free, delayed-action adhesive to allow time for repositioning. Covers are environmentally-friendly with recyclable release liners. 25 covers per package