The answer to mailing bulky items, books or spiral bound materials.  Expand-A-Mailer available in increments of 1 case - 4 sizes available: 10"x7-3/4" - 12-1/2" x 9-1/2" - 15" x 12-1/2" - 17" x 14" • The First Dimension for each mailer listed below is the size of the opening. • Attractive white mailer makes a great impression. • Convenient side loading mailers make fulfillment a breeze. • Peel and seal closure keeps contents secure during shipment. • Mailers feature a pull tab strip for easy opening. • Made from 100% Recycled paperboard.