Office Max #8-5/8 Double Window Business Envelopes, 24 lb White Wove, 500 / box Check-size envelope is compatible with most standard 3 1/2" x 8 1/2" checks and payroll and accounts payable forms #9 envelope is compatible with most standard 8 1/2" x 11" computer generated invoices and statements Side-seam construction 24 lb white wove 500 per box