Sunshine Kids Radian XT Convertible Car Seat The Radian XT is a convertible car seat for children 5 to 80 lbs in a 5-point harness. Safety features on this car seat include superior side-impact protection with steel alloy frame, adjustable reinforced head supports and energy absorbing foam. Carry on your shoulder or as a backpack, RadianXT folds flat for travel convenience. Roomy seat interior provides more inside shoulder room while narrow outside profile allows RadianXT to fit 3 across a back seat. Comfort features include thick memory foam padding, infant support cushions for head and body and padded carry strap.