Convertible Car Seats are used in a rearward-facing position until your child’s shoulders reach the lower shoulder height marker and should be at least 6 months old. The Convertible Car Seat then can be used in the forward-facing position until the shoulders reach the upper shoulder height market (approx. 4 years of age). Some Convertible Car Seats will allow your child to stay in their car seat up until the age of 8. Britax Safe-n-Sound and InfaSecure have a great range of Convertible Car Seats.