No. 10 Left-Side Window Redi-Seal Envelopes provide dependable performance, strength, durability and privacy. Redi-Seal closure requires no moisture, extends shelf life and produces a secure seal. Double-flap design keeps the gum from sticking before use. Left window conveniently accommodates a printed address, eliminating handwritten addressing. 24 lb. bright-white stock and side seams give mailings a professional look.