We are pleased to add this Self-Adhesive Cardboard Envelope Mailer for #10 Envelopes, pack of 750 to our product line at CollecTons. This Cardboard Envelope Mailer is designed to fit perfectly into a #10 envelope (the standard business-sized envelope which measures 4 1/8" x 9 1/2.") The self adhesive flaps of the Cardboard Envelope Mailer fold together and around the contents and provide additional protection and security for mailed items. Each Cardboard Envelope Mailer is printed with the phrases "Attention!!!" and "Merchandise Enclosed."