A Friend Knows $20.00 Inside Message Inside: Where to Land 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". A Friend Knows quantity Add to cart SKU: 714. Categories: Friendship & Support, Pets. Related Products Chocolate for My Bud $20.00 Beyond Words $20.00 Everything is Within Reach $20.00 Friends Keep you Growing $20.00