It comes with three swaddle sizes, though you can buy additional ones if you'd like. The short answer, according to the brand ...

This combines a gentle rocking bed with soothing white noise and snug, safe swaddling, with 5 levels of specially designed sound and motion that imitate the calming sensations of the womb.

Swaddle too loosely – and your baby may ... a little practice – you'll quickly help your little one be the happiest baby on YOUR block. For WebMD, I'm Dr. Harvey Karp.