The Pioneer 12" x 12" top loading page protectors may be the most versatile page protectors you'll ever find. They are made as refills for Pioneer Memory Albums, but they will also work in most post bound, three-ring or strap-hinge albums. Made of acid-free, lignin-free and PVC-free materials, they are extremely durable. You don't have to worry that your album will come apart as you're flipping through your pages. This pack of 5 refill page protectors (10 sides) are made of seamless, clear polypropylene. They come with heavy white paper scrapbook inserts and two post extensions. These page protectors are designed for Pioneer Memory Album MB-10, FTM-12, BF-12, TM-12, and WF-12 and most post bound or three-ring memory books.