#1 Rated Infant Car Seat in America! The Chicco KeyFit Infant Car Seat is the premier infant carrier for safety, comfort, and convenience. The KeyFit is packed with features that make this Infant Car Seat the easiest to install and thus the safest choice for your baby. Designed especially for the Chicco KeyFit Infant Car Seat, the Cortina Stroller works as a travel system for your infant and a full-size stroller for your growing baby. The Cortina Stroller will satisfy your desire for convenience, comfort and safety.