Just a Little Mistake $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". Just a Little Mistake quantity Add to cart SKU: 468. Categories: Baby - Parenting, Sympathy - Healing. Related Products Haven’t Seen You in Many Moons $20.00 Baby with bike trailer $20.00 Give Peas a Chance $20.00 Never Look Back $20.00