Child car seat series britax rmer kidfix sict carry weight 15 36 kg age 4 12 years group 23 with isofix side impact protection harness system 3 point safety harness padded seat belt padded clasp exterior measurements 68 86 x 54 x 42 weight 72 kg adjustable backrest central belt adjustment height adjustable colour blue seat reducer cover material polyester slip cover washable cover