H0051 HCFA Blank Envelope Self Seal Right Window Size: 9 1/2 x 4 1/8″ Perfectly sized and aligned to accept HCFA claim forms. Perfectly sized and aligned to accept HCFA Claim Forms. 24# White Stock Window size: 4 1/2 x 1 1/8″ Window alignment: 4″ from left, 1 3/8″ from top of envelope. Tinted inside pattern prevents private information from showing through.Black security tint inside. Self-sealing: Saves time and makes mailing easier. Adhesive has 6-12 month shelf life 500 per pack