Make naptime and bedtime extra comfy with the pediatrician-designed Happiest Baby SNOO Sleep Sack, designed for use with the SNOO bassinet (sold separately). The innovative zip-up sack is thoughtfully designed with wings that slip onto the SNOO's clips to keep little ones bundled up and on their back all night long. Babies will stay at a comfortable temperature, thanks to the breathable mesh panels at the shoulders and waist. And the swaddle will transition as baby grows—snaps at the shoulders let them sleep with one or both arms free.