Quality Park #9 Security Envelopes are designed to fit QuickBooks computer generated invoices and statements. These #9 envelopes (not for QuickBooks checks!) are also often used as reply or return envelopes in business mail. Our business envelopes have careful window placement to show only the sender and receiver addresses while social security numbers and other data remain private and protected. For privacy, our security envelopes have a reflex blue tint with safety pattern to prevent prying eyes from reading sensitive information, even when held to light. You won't miss licking the gummed seals on basic envelopes. Our Redi-Seal self seal envelopes are a tidy, timesaving upgrade — just raise the lower flap and press for a no-fuss seal. 24 lb white wove paper with side seams give Quality Park envelopes a professional appearance. These bright white safety envelopes are perfect for payroll, accounts payable and all sorts of confidential business applications. Stock up and get more for your buck; bulk boxes of 500 security envelopes are made for high volume envelope users. Ideal for accountants, law offices, or any workplace or small business that moves large volumes of mail. Envelope dimensions are 3-7/8 x 8-7/8 inches. Top window dimensions are 1-3/16 x 3-1/2 inches, 3/8 inches from the left and 2 inches from the bottom. Bottom window dimensions are 1 x 4 inches, 3/8 inch from the left and a 1/2 inch from the bottom.