Security Invoice Envelopes: Forget the thin, torn easily and see-through envelopes you used in the past, try our ValBox #10 security envelopes, which fit QuickBooks invoices, multiple business billing statements and return envelopes perfectly!!! The contents are also easy to slip in..Double Windows Design: The windows line up perfectly with return and sender address, eliminating the need for hand addressing or printing mailing labels, ideal for legal and standard business mailings, return documents and more. The detail position for the double windows, please refer the size chart on the second photos. Notice: This #10 double window envelope is not for QuickBooks Checks!!!.Premium Quality: These #10 double window envelope features with durable 24lbs white wove paper, peel-off strip, stronger glue and security tint design. Protect your invoice and statement privacy..Great Self Seal Envelopes. The self-seal feature makes these envelopes with windows much more convenient than regular, moisten-and-seal ones. You don't need to stand licking envelopes and using glue or the water activators, which is time consuming and messy..Strong Adhesive: With the strong adhesive flap, ValBox #10 double window envelopes will be more evident if tampered. No need to worry about opening them easily by others. If there's anything make you unhappy or unsatisfied about the products, please do contact us without any hesitation.