Finally, the car seat that parents have been searching for is here! Our Nautilus?3-in-1 car seat helps keep your child secure from 20 to 100 lbs. Nautilus?is a 3-in-1 car seat that converts from a harnessed booster to a high back belt-positioning booster and finally to a backless belt positioning booster. The harness booster can be used up to 65lbs, and as your little one continues to grow, the Nautilus does too, transitioning into a Highback belt positioning booster which can be used from 30 - 100lbs, and finally into a Backless belt positioning booster for a comfortable fit from 40 to 100 lbs. This is totally one of the best car seats to get for children. You will not regret buying this because you know that your child will be safe.