Upper & Lower Adapters for Z4 / YPSI stroller. Allows you to attach Companion Seats, infant car seats, bassinets or any combination. IMPORTANT: The Z4 / YPSI Double Adaptor allows you to convert your Z4 or YPSI stroller to a combination of stroller with Nido infant seat, or stroller with bassinet or stoller with 2 seats. Nido, Bassinet and Second Seat are sold separately.