Double Window First Class Envelope (Moisture Seal), 6" x 9", #PED04 - Forms & Fulfillment
Amazon.com : Universal UNV36300 3.63 in. x 8.63 in. Square Flap Double Window Business Envelopes - White (500/Box) : Envelope Mailers : Office Products
What are double envelopes? — Shore Thing Stationery
Office Depot Double-Window Envelopes, #10 (4 1/8in. x 9 1/2in.), White, Gummed, Box Of 500, 12018 - Walmart.com
Business Envelopes - Double Window Confidential Self Seal Envelope - 5022C by Deluxe | Deluxe.com