Happiest Baby GUC Sweetpea 5 Second swaddle sack Size Large: 18-26lb 💯 Organic Cotton Life saver once baby started breaking out of his swaddle. “#1 Swaddle” New York Times: Rated America’s best baby swaddle, our Sleepea was designed by top pediatrician and the world’s leading swaddling expert, Dr. Harvey Karp. Perfect for healthy, growing hips (International Hip Dysplasia Institute seal of approval).