Viv - I have the Baby Bjorn Air and the Active one....I find the active one hurts my back but the air one doesn't. I suggest going to maybe Babies Galore at Parkwood and trying them all out with James and walking around the store. Rhys has been in the Crawlers for 3 weeks now!! I bought a box yesterday. I don't know how much he weighs at the moment but I am pretty sure he is almost at the 8kg mark. He was 7.4kg 2 thursdays ago.