Companion Bike Seat frames are made with chromoly steel tubing, and were load tested at over 4000 lbs. The 200 lb max load capacity of the bike seat is based purely on the limitations of your bicycle, most of which are rated between 300 and 350 lbs max. Companion Bike Seats are comfortable for passengers of all sizes, and transform your existing bicycle into a cargo bike with locking storage and an extra seat.