These are clear vinyl CD sleeves. The sleeves have an adhesive back so they can be stuck to the inside of books. These are the same sleeves college textbook companies use to hold the CDs in books. The sleeves measure 5.25" wide and 6" tall. Simply slip disc in the back of sleeve, peel off the two backing pieces, and lay your CD sleeve in your book or on any flat surface! The perforated front allows for a tamper-proof design, making it clear that the discs inside are new and have not been used!