#10 SINGLE WINDOW ENVELOPES: EXTRA LARGE WINDOW FOR PREMIUM MAILING! Ideal for bulk mailing, each envelope is designed with an extra-large, easy read 4-1/2 X 1-1/8 poly window, positioned 7/8" from the left and 1/2 from the bottom of the envelope, perfect for displaying mailing addresses and eliminating constant hand addressing and printing for cheaper, quicker bulk mailing! - Extra-large, high visibility, easily read front window, perfect for addresses. - Perfect for mailing Invoices, QuickBooks Invoices and checks, billing statements, checks, and other business mail. - 500 envelope supply with each measuring 4-1/8 x 9-1/2 inches.