These envelopes are great for bulky catalogs or oddly shaped items that come through the mail room. They're built from durable Kraft paper with an impressive 2" expansion to accommodate larger shipments, plus open-end, reusable split regular gum adhesive. Together, the secure seal & expansion slot provide increased productivity & peace of mind. Seam Type: Center; Flap Type: Square; Trade Size: #15; Security Tinted: No.