Featuring a horizontal orientation and booklet-envelope design, Pendaflex Poly String & Button Envelopes are ideal for storing and transporting frequently referenced documents. Durable polypropylene construction is wear-, tear- and water-resistant. Fold-over flap along with a string and riveted button closure help ensure your documents stay secure and protected from the elements while in transit. Manufactured acid-free for archival-safe storage. 1.25" Expansion250 sheet capacity. Seam Type: Weld; Flap Type: Square; Security Tinted: No; Opening: Open Side.