Quality Park Health Claim Insurance Envelopes for Medicare Form HCFA-1508 - Security Tint - Single Window - 9" Width x 12 1/2" Length - 28 lb - Self-sealing - White - Wove - 100 / Box 9" x 12-1/2" Health Claim Insurance Envelopes simplify mailing preparation. Durable, claim form envelopes are made of 28 lb. white wove stock to withstand extensive handling in transit. First-class border lets your recipient know that something important is in their mailbox. Contents are protected during use to give you assurance that they arrive unharmed. 9" x 12-1/2" size accommodates forms without folding. Single window displays an address. Moisture-activated flap features deep gumming for a secure seal. Envelopes are perfect for Medicare Form HCFA-1508 and other healthcare forms.