Box of 100, HCFA Envelopes W2A38821C, Window Style, 4-1/2 x 9-1/2″, Gummed Flaps ( Moistening Required),. No. 10 1/2 envelopes are designed for use with Insurance Form CMS-1500 and similar forms. The 1-1/8″ x 4-3/4″ window positioned 3-7/8″ from the left and 1-1/2″ from the bottom of the envelope. Inside security tint offers more privacy. 24 lb