Quality Park #10 1/2 Healthcare Claim Form Envelopes are for CMS-1500 and other insurance forms. The reflex blue pattern protects sensitive information because it obscures the details of the contents, even when held up to light. These 24-lb white wove envelopes can be used for professional mailings; side seams provide a more modern, clean look. The single window measures 4.5" x 1" and is positioned 4.25" from the left edge and 1.56" from the bottom. This allows for a name and address without revealing other personal information on the claim form. Stock up on boxes of 500 for bulk mailings.