S = 500 envelopes M = 750 envelopes L = 1,000 envelopes. This No. 10 Security Double-Window Envelope features dual windows that allow for direct visibility of address information, making it ideal for mailing a wide variety of business correspondence, invoices, bills, and checks. The envelopes are equipped with a self-adhesive closure strip that creates a secure seal across the width of the envelope, eliminating the tedious steps of applying glue or licking this enables fast, efficient processing for bulk mailings. The interior features a granular security pattern and dark tinting designed to effectively prevent contents from showing through, ensuring that the letter's contents remain shielded from prying eyes and fully safeguarding privacy. Each box contains 500 envelopes, providing a supply sufficient for long-term use and making this product an ideal choice for both daily business correspondence and large-scale mailing tasks. Weight: 6.23 lbs.