Open-Side Booklet Envelope, #15, Hub Flap, Gummed Closure, 10 x 15, Manila, 100/BoxEmbellish Quality Park Open Side Side Seam Booklet Envelopes with logos, labels and more. The crisp, white wove paper is available for printing to coordinate with the contents inside, whether that be a promotional booklet or shopping catalog. A classic, solid gum adhesive seals the envelopes closed and keeps everything secure until it lands in the recipient's mailbox.