Our COMFORTmodel is often used by parents with a baby from 7 months. Your child can already sit or making an attempt to do so. During the ride baby’s from 7 month still need support to get through the curves and bumps on the road. Designed with a sleeping position, the seat prefents leaning of the head on the chest while sleeping. Our comfortmodel 4-S is often used by parents who take their baby for long rides into their biketrailer or childrentransportbike or for daily use! Perfect for parent who leave the seat outside in their transportbike! Our COMFORT 4-S model consist of an EXTRA FOAM CUSHION under the cover AND at the sides as well! That is the only difference between our basicmodel.