Keter Kid's Poly/Cotton Tzitzis with Round Neck and 1 hole for the tzitzis strings. Size 2 measures approximately 12 inches long from the shoulder to the bottom of the garment, size 3 is 14 inches long, size 4 is 16 inches long, size 5 is 18 inches long, and size 6 is 19 inches long.
I'm giving a little unasked for general advice, check all tzitzis to be sure there's no defect in the knots.