Columbian #9 Double-Window Security Envelopes are designed to fit computer-generated invoices and business statements. Double windows are precisely aligned to keep your recipient's personally identifiable information concealed. Windows are positioned 3/8" from the left edge. Top addressee window measures 1-1/8" x 3-1/2". Bottom recipient window measures 1" x 4" with 1/2" space between windows and the bottom edge. Compatible with most common laser printed invoicing software. Our security tinted envelopes have a privacy tint and a complex security pattern. Both help obscure the appearance of letters and numbers. Keeps social security numbers, payroll checks and private data hidden, even when held to light. Moisture-activated gummed seal provides a reliable closure that's approved for use with automatic mail inserters. Open-side diagonal seam envelopes are made from classic 24 lb white wove paper. Stock up now for the year's monthly invoicing. #9 Envelopes measure 3-7/8 x 8-7/8 inches. 500 Per box.