All Orbit Baby seats and stroller frames are designed to be compatible, with a few exceptions:
Car Seat Bases: Please note that you may only use Orbit Baby car seats (infant car seats and toddler car seats) on the car seat base in the car. You may not dock any Orbit Baby bassinets or stroller seats onto a Car Seat Base or use them in the car.
Generation-one car seat base: If you own a pre-2009 generation-one Orbit Base (a discontinued product), you may need to update it to extend its use to the Toddler Car Seat. Check here for more information.
Stroller Frame G2: May be used with all generation-one and G2 seats.
Generation-one stroller frame: May be used with all generation-one and G2 seats; note that when using the Stroller Seat G2 on the generation-one stroller frame, you must install a piece that came included with your Stroller Seat G2.
Double Helix Stroller Frame and Helix Plus: Either SmartHub may be used with any Orbit Baby seat, except that you may not use a Toddler Car Seat (generation-one or G2) on the rear SmartHub of your Double Helix Stroller Frame or Helix Plus Upgrade Kit.