Quality 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. These 24 lb white wove envelopes have side seams for a clean, professional look.