Compatible with Radian 3RXT SafePlus, Radian 3QX and Radian 3QXT. As your child grows the SafePlus steel anti-rebound bar increases stability and reduces rebound rotation by up to 50%, so you can keep them in a safe rear-facing convertible car seat for longer (up to 50 lb / 22.7 kg). Pair with Anti-Rebound Fabric Bar Cover (sold separately) for use in warmer months as the anti-rebound bar can get hot to the touch.