Far and away the easiest swaddle you'll ever use, the Sleepea was designed by famed pediatrician and sleep expert Dr. Harvey Karp to provide just the right amount of pressure to get babies to relax. It has an inner layer with velcro to hold baby's arms in place, and the exterior layer hugs a bit on top, but has a loose bottom for hip safety.A two-way zipper makes for easy changes, and the whole thing is machine washable and dryable, and it just gets softer and softer the more it's laundered.