The Kiddopotamus Snuzzler does an excellent job keeping baby from slumping in seats and swings. It can be used with just about any kind of buckle/harness including 5 point, 3 point, and typical swing belts. The Kiddopotamus Snuzzler is safe for use in car seats. It is designed so that the padding is to the side of the baby and NOT behind the baby. Kiddopotamus Snuzzler is specially designed with padding only on the sides of baby's head and body, not in back of baby, for proper harness fit." This meets the requirements of the National Highway Traffic Safety Administration which states "Never place any extra cushioning under or behind your baby. This also prevents harness straps from being snug." The NHTSA also recommends using towels to support baby's head and neck, but the Snuzzler stays in place better because of its design and, therefore, in my opinion, would be safer to use than towels. Also, the NHTSA recommends not putting jackets and heavy clothes on your baby in a carseat because this also prevents harness straps from fitting properly. The Snuzzler is designed with warm fabric on one side and a cooler feeling fabric on the other side to accomodate seasons, keeping baby warmer in colder temperatures and cooler in warmer temperatures, decreasing the need for bulky coats and clothing in the winter.