Online Help Our two large automated inserters can automatically insert up to a 6" x 9" envelope with up to 6 inserts in one pass, seal and meter. This includes the most common #10 regular sized business envelope. For non-standard sizes that will not fit the inserter, our hand inserting and fulfillment department can handle any job, large or small. Just call a Drive Thru direct marketing expert today at 800-850-2248 with your specifications and we'll assist you in determining the best, most economical way to mail.