The spacious and sturdy modular design of the Peg-Perego Triplette Piroet Chassis directly accepts Peg-Perego Primo Viaggio car seats and Pop-Up stroller seats (sold separately) to create an easy to maneuver and push inline stroller for up to 3 children. Peg-Perego's Triplette Piroet Stroller Chassis features a spacious and versatile modular design that serves as a foundation for a comfortable and easy to maneuver inline stroller for up to 3 children.