Peg Perego YPSI Stroller with Double Adapters The Peg Perego YPSI is a compact single-to-double stroller compatible with all Primo Viaggio 4-35 infant car seats. To configure it for twins: • Start with the YPSI stroller • Add the YPSI Double Adapters • Attach two Primo Viaggio Lounge car seats LTKBaby LTKFamily LTKTravel