Easy Pres-Stik Self-Sealing, Nothing to Peel Standard No. 10-1/2 (4.5" x 9.5") White Side Seam Window Envelopes for G-38 Claim Forms Inside with Blue Security Tint 500 Envelopes Come in Unwieldy, Reusable, Cool, Reclosable Box CMS-1500 (HCFA) Self-Seal G-38 (3880) Window Envelopes for Health Insurance Claim Forms, (No. 10-1/2) 4-1/2" x 9-1/2", White with Inside Security Tint - BIG BOX OF 500 ENVELOPES