Pack of 500 envelopes offers you ample supply for bulk mailing needs No. 8-5/8 check envelopes feature double windows, allowing both the return and mailing addresses to be seen clearly Poly windows and inside tint protect your documents, ensuring the contents remain private A unique self-sealing, double-flap design prevents premature sticking, keeping the gum fresh until you're ready to seal Made from sturdy 24lb. paper, these envelopes seal securely without needing moisture To seal, simply lift the lower flap and press, completing the process in seconds