Flower Letter $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". Flower Letter quantity Add to cart SKU: 564. Categories: Friendship & Support, Gardening. Related Products just add flour $20.00 We Grow Together $20.00 Paws in the Flowers $20.00 A New Pea $20.00