less than 20 pounds, some no less than 22 pounds, in a forward-facing position. As of 2011, most children ride rear-facing until they are at least 2 years of age. The National Highway Traffic Safety Administration (NHTSA) advises the use of a child restraint or a booster seat for all children who are shorter than 4 ft 9 in, regardless of age and weight, or even longer if the belts hit the child at the wrong place. Some booster seats can be used for children up to 60 inches and 120 pounds. Many state laws prefer that children 12 years and younger sit in the back seat if available. Some states, as is the case in Michigan, forbid placing a child under the age of 4 years in a front seat if a rear seat is available. Some states require that all child safety seats be used in full accordance with the manufacturer's instructions in what is sometimes referred to as a "proper use clause". Manufacturing Though there are hundreds of variations of makes and models in the world of child safety seats, the materials used in the manufacturing process are basically the same. Factories in which the seats are put together receive loads of polypropylene pellets. Foam makes up the padding of the individual seats, while vinyl and fabrics are used to make up the covers for the seats as well as the harnesses. A safety seat increases the safety of a properly restrained child in the case of a motor vehicle accident. The safety seat includes foam padding, fabric covers, a harness, and buckles or attaching mechanisms. Labels and instructions are also attached. Every child safety seat will have an expiration date on it. The Safe Kids USA organization does not recommend using a child safety seat that is more than 6 years old. Periodically, child safety seats are recalled by manufacturers for safety reasons. The National Highway Traffic Safety Administration posts a link to recent recall information at nhtsa.gov. Types There are different types of child safety seats for children of different sizes and ages. Infant seats - Child safety seats made specifically for infants are the smallest and have carrying handles for easy carrying and loading. Newborns are most often placed in a rear-facing seat. These seats are designed for infants is up to , depending on the model. Convertible seats - Similar to the infant