Size S = 500 Envelopes Size M = 750 Envelopes Size L = 1,000 Envelopes. No. 10 Security Envelopes: Featuring a single-window design, these envelopes are ideal for business and legal correspondence, invoices, or confidential documents requiring a high level of security. The interior of each envelope is printed with a security pattern to effectively safeguard data privacy. The left-aligned window design is clear and legible, allowing the recipient's address to be displayed directly this not only protects the contents of standard business letters but also eliminates the tedious task of handwriting addresses.No glue sticks or moistening are required, significantly boosting mailing efficiency-making them particularly suitable for bulk mailings and helping you save valuable time. With a reliable, long-term supply available, each box contains 500 envelopes, making them an ideal choice for both home and office environments. Weight: 6.6 lbs.