Staples Fold-and-Stick #9 Double Window Security Envelopes - 3-7/8" x 8-7/8" - White - 250 PackSend important mail with confidence with Staples Fold and Stick #9 Double Window Security Envelopes. Ideal for business correspondence, these envelopes are a great choice for various letters, statements and invoices. Quick and easy to use, they feature a fold and stick closure that doesn't require moisture. Simply raise the lower flap and press it to the upper flap to seal. The white envelopes are designed with a square flap and side seam that allows