yeh we got the hi pod brand that has the headrest that goes taller as it was dramatically cheaper and allowed for taller children and thus they were able to stay in the same seat until they are older. my understanding is that the built in clip on all models (maxi rider or hipod or ??) goes until 18kg and then you needed a harness (whether it be straight H or the one that is about $10 more and splits to go through the shoulder slots in the seat) or normal seatbelt after that anyway. I used the harness initially but have changed it now to just a booster with seatbelt for my oldest cause hes taller hipod are also slightly narrower than the maxi rider.