#10 SECURITY ENVELOPES. These 4 1/8" x 9 1/2" inch envelopes are designed with security print to protect contents and sensitive information, perfect for protecting sensitive information from others. SECURE. Just peel and seal to create a strong lasting seal without licking or moistening. Our self seal design is quick and easy and is guaranteed to stay sealed with no need for tape or glue sticks. WINDOWLESS DESIGN. Envelopes manufactured with a windowless front panel for easy printing, labeling or hand-addressing, perfect for quick, mass business mailings. WHITE 20LB STOCK. Perfect for everyday business use, these standard white envelopes are crafted of heavy, durable 20lb paper and securely holds hefty files during transit. MULTI-PURPOSE. These envelopes can easily fit invoices, letters, checks, gift cards, etc. These envelopes can be used for virtually anything you need them for!