The BikeSmart BarNone Frame Adapter is an ingenious solution for carrying bicycles that don't have standard top tubes on rear-mounted car racks. The heavy-duty, spring-loaded clamps attach to the bike at the stem and seatpost, creating an effectively-straight top tube to suspend from the car rack. The frame adapter works with most full suspension frames, step-through frames, and kid's frames. Weight limit: 35 lbs