Quality Park Security Tint HCFA Window Envelopes, Gummed, White, 4.125 x 9.5, 500 per Box, (21439) CMS-1500: This window envelope is specifically designed for Healthcare Claim Form CMS-1500 and similar forms GUMMED: Fully gummed flaps provide a secure seal to keep contents secured SECURE: Protect sensitive client information with these security tinted envelopes. The reflect blue tint pattern makes it impossible to see the details of the contents, even when held up to the light STAY AWAY FROM MOLD AND MILDEW: This envelope is made with a material that inhibits the growth of mold and mildew to protect the product and its contents GREAT VALUE: Conveniently packed in 500 count to reduce the frequency of repurchasing