The car seat adaptor for the city select allows you to use your car seat with your city select stroller it is designed to fit several popular car seat models including the following maxi cosi cabriofix carseats be safe izi sleep or izi go carseats to configure for two car seats the second seat for the stroller or a set of double adaptor brackets must be purchased in advance as these brackets are required to support the second car seat please note car seat and frame not included