The use of our Double adapters enhance the sleek and compact design of the YPSI or Z4 stroller. The double adapters take away the limitations that most double strollers offer by giving the parent's a choice on the style that works best for the family. Create the double stroller of your dreams by paring these easy to use double adapters with any Peg Perego Ypsi Stroller, companion seat, Ypsi bassinet, and Primo Viaggio 4-35 Nido car seat. Includes both the upper and lower set of adapters. Install once with no need to remove them again.