There are several things to consider when purchasing a Dust Jacket Cover, also called Book Jacket Cover and Mylar Covers (although covers are not actually mylar).   The Main consideration is the Type of Book Jacket Cover.  The summary below highlights the differences between the two types Archival Quality and Non-Archival Quality.

Archival Quality: Can be used on ANY book and is preferred by book collectors.
The easiest way to tell the difference between Archival & Non-Archival is to look for printing on the paper Backing. If there is printing present, it's NOT archival. With Archival Quality, The paper backing, clear film and the adhesive used to fasten the film to the backing are all formulated to meet Archival Specifications.                 

• The paper is acid free with NO printing.
• The film is chemically stable polyester (lots of people call this Mylar in error)
• The adhesive used to bind the paper to the clear polyester is pH neutral (no migrating acids).
• There are NO sticky adhesive strips to hold the fold shut. Over time the sticky adhesive can (and does) migrate on to the Book or DJ.
• All of these combined make for a long lasting book jacket cover that will not yellow or crack, acids will not migrate to your book or DJ. Since there is no ink, there is no acid migration or ink bleeding through to your DJ or Book.

Non-Archival:

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Determining the Correct Size of  Book Jacket Covers for Your Books:

Step 1:  Measure the height of your book or Dust Jacket. 

• Then choose the size that is the closest match to the height of your book or a few inches taller. 
• You can always fit a shorter book to a DJ cover, But not a taller one

Step 2: Measure the length of your Dust Jacket.  .

• The standard length sheets will cover most books
• If your book/DJ is very wide, thick or very narrow, Then purchasing a roll will be your best option.  With a roll, you can cut the Book Jacket Cover to YOUR Specifications.

If you have any further questions, you are always welcome to contact us through the contact the seller link.