Combi Shuttle 33 Seat BaseStay in step with your active lifestyle by keeping an extra base in your family’s second car or even Grandma’s car. This sturdy base is easy to install and is designed specifically for the rear-facing Shuttle 33 Infant Car Seat. When an extra car seat base is necessary, the new Combi Shuttle 33 Seat Base is a lightweight and portable way to make your life easier.