From - http://wereparentsblog.com/tortle-beanie-prevent-flat-head-syndrome-review-giveaway/
TORTLE!? What is a tortle you may ask? I know I did. A Tortle is a simple, comfortable beanie that helps prevent early stages of flat head syndrome (plagiocephaly and torticollis). This beanie helps make the job of re positioning babies safe and easy. It works by gently deflecting your baby’s head when lying on the back of her head. Since the back is now known to be the safest place for baby to be, flat head syndrome has increased by 600% (since 1992).
It is used when baby is awake by placing the beanie on your baby. Align the support roll behind one ear then switch sides at every feeding. It is not intended for overnight use. It is an FDA-cleared Class I medical device. Made from 95% cotton and 5% spandex. It comes in 3 sizes S (0-2 months) M (2-4 months) and L (4-6 months)"