Send Yourself a 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". Send Yourself a Letter quantity Add to cart SKU: 486. Category: Friendship & Support. Related Products Share an Umbrella $20.00 Hi $20.00 A Friend is Like a Quilt $20.00 May You Always have Tailwinds $20.00