Quality Park Double Window Envelopes display both sender & receiver addresses for mailing statements & invoices. Features a special Redi-Seal self sealing closure. Simply lift the bottom flap & 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. Heat-Resistant Adhesive. Seam Type: Diagonal; Flap Type: Commercial; Trade Size: #8 5/8; Security Tinted: Yes.