Christmas to the Core $20.00 Inside Message Blank Inside Packages of Heartstrings® cards are shrink-wrapped and sold in sets of 10 cards with envelopes. The actual card size is 4 1/4" x 5 1/2". Christmas to the Core quantity Add to cart SKU: 690. Category: Christmas - Holiday. Related Products High Hopes $20.00 The Season to Remember Your Roots $20.00 Oh What Fun It Is to Ride $20.00 Everything’s Gonna Be All White $20.00