What product specs for letters do you have available? 8.5” x 11” B&W Document Specs 60# text/89gsm paper #10 2-window outer envelope 8.5” x 11” Color Document Specs 60# text/89gsm paper #10 2-window outer envelope Related articles What product specs for letter envelopes do you have available? What does the address_placement parameter mean? What are your mailing class options? How can I export my letter data? Does Lob support custom envelopes?