DOUBLE WINDOW SECURITY ENVELOPES; tired of cheap paper envelopes that can be easily seen through?. Double Window QUICK-SEAL Envelopes are the perfect envelopes for you! Each envelope contains two front windows, a 1-3/16″ X 3-1/2″ top window positioned 3/8″ from the left and 2″ from the bottom and the bottom 1 X 4″ window is 3/8″ from the left and 1/2″ from the bottom.