You can buy booster seats that are simply the cushion part. But some Group 2/3 car seats also convert to a booster cushion for Group 3 mode. Essentially, this removes the seat's protective sides (Group 2) and turns the seat into a booster cushion. There is no specific booster car seat age to begin using one. Instead, many parents switch to car booster seats when their child outgrows their rear-facing child car seat. So, the age for starting booster car seat use is often around four years old. A booster seat can help to raise a child's body to a height suitable for using the adult seatbelt. Some have ‘horns’ that help the car’s adult seatbelt to sit across your child’s tummy. may be wondering whether they need to switch to a booster car seat and, if so, which one to buy. Here we will give you the lowdown on booster car seats and share 20 of the best booster car seats for 2023 available to buy right now. What is a booster car seat? Booster car seats usually fit into the Group 2/3 and Group 3 car seat classifications. These groups specify the recommended weight of a child that can safely use a booster car seat.If you want to keep your child in a child car seat for as long as possible for safety reasons, but they’ve reached or exceeded the 135cm/4ft 5in height threshold, there are still some options.