With a few simple snaps these brackets can turn your City Select Single into a City Select Double! The brackets allow you to attach a second seat or a car seat adapter in the lower position, giving you the ability to fully customize your City Select. (Second Seat Adapters are included in the Second Seat Kit) This item makes it possible to purchase just the City Select stroller and use your car seat for the second child. Without this, you would need to purchase the full second seat kit to use a car seat adapter for the second child. If you did purchase the second seat kit you will not need this accessory as it's included in the second seat kit.