No. 10 Double Window Security Tinted Envelopes use a self-seal closure for the ultimate convenience. Side seams add a modern, professional touch to your mailing. Convenient, Redi-Seal closure requires no moisture and has no pull-off strip to throw away - just unfold the bottom flap and press for a secure seal. Premium security tint ensures privacy is preserved during mailing. 24 lb. bright-white stock gives mailings a clean, crisp look. Left-side, double windows are perfect for displaying sender and receiver addresses.No. 10 Double Window Security Tinted Envelopes use a self-seal closure for the ultimate convenience. Side seams add a modern, professional touch to your mailing. Convenient, Redi-Seal closure requires no moisture and has no pull-off strip to throw away - just unfold the bottom flap and press for a secure seal. Premium security tint ensures privacy is preserved during mailing. 24 lb. bright-white stock gives mailings a clean, crisp look. Left-side, double windows are perfect for displaying sender and receiver addresses.