Envelope is designed to be compatible with most computer generated forms, invoices, purchase orders and more. Two Poly-Klear windows clearly show return and mailing addresses from contents eliminating the need to address envelope. Features: Convenient and secure self-sealing Grip-Seal closure. Simply peel off release strip and press down for a quick, secure seal. Security tinted for added privacy and confidentiality. Premium 24lb white wove stock. Top Window: 1 x 3-1/2 Inches, positioned 1/2 Inches from left, 2-1/2 Inches from bottom. Bottom window: 1-1/8 x 4 Inches, positioned 1/2 Inches from left, 3/4 Inches from bottom. Sized: (#10) 4-1/8 x 9-1/2 Inches. Quantity = 500 envelopes.