Open a window to Christmas joy! Send Advent Calendar Cards. Here is an exciting new way to send a Christmas greeting because it's more than a card. Open a window a day to reveal, behind each of the 24 windows on the front of these cards, important symbols and pictures--as well as a Bible citation--highlighting the true meaning of Christmas. Send some joy through the mail! 4-3/8 x 6-1/2. 20-pack. Envelopes included.