The Baby Tuck Sheet is a TOG-rated, safe alternative to blankets suitable from birth. Designed to use over the top of a swaddle or sleeping bag, the Baby Tuck Sheet is a firm-fitting mattress sleeve that provides added security and comfort for a newborn during sleep. The zips allow you to adjust to two levels of firmness (tightness), to find the perfect fit for your baby's size, or strength of startle reflex. The Baby Tuck Sheet has been stringently tested and approved as safe by leading independent infant safety organization INPAA. When using the right size for your baby's length and sleep environment, the Baby Tuck Sheet will not come up higher than mid-way up baby's chest following Red Nose safe sleep guidelines. Given the design of the product, the Baby Tuck Sheet cannot become untucked from the mattress, be pulled up near baby's face, or be classified as loose bedding in any way. Newborns who don't like to be swaddled may find the firmness of the Tuck Sheet comforting in lieu of sleeping with their arms in. Please do not use the Baby Tuck Sheet once your baby shows signs of rolling over.