Double Window Redi-Seal Security-Tinted Envelope, #9, Commercial Flap, Redi-Seal Adhesive Closure, 3.88 x 8.88, White, 250/CTQuality Park Double Window Envelopes display both sender and receiver addresses for mailing statements and invoices. Features a special Redi Seal self sealing closure. Simply lift the bottom flap and press to the top flap for an instant, secure seal. A reflex blue pattern protects sensitive client information because it obscures the details of the contents, even when held up to light.