With the CYBEX Sibling Seat, you can convert the e-Gazelle S and Gazelle S strollers (sold separately) from a single to a double to grow right alongside your family. The full-size e-Gazelle/Gazelle S seat can be used in parent-facing or forward-facing mode, and it can be attached to either stroller's upper or lower position. Its one-pull harness helps you quickly secure your little onesa game-changer when you're strapping in two!