The Bettendorf Double Truss Truck was introduced in the 1930s by U.S. railroads and was allowed to be used in interchange service through 1993. The Kadee #500, #502 & #550 represent 50 ton trucks for 100,000 pound cars, Self-centering action trucks self align themselves parallel with the car for easier placement on track. Mounts with a #2 or 2-56 screw. 2-piece fully equalized trucks. 1pair. Truck features: *Self centering action *Code 88 (.088) 33′ smooth back wheels *HGC weighs nearly the same as metal trucks *Superior rolling ability *Brake pads * Accurate markings *Incredible detail true to prototype *Non-magnetic metal wheels *Highly flexible fully equalized trucks *Smooth-tracking free-rolling contoured insulated axles *RP-25 free rolling wheels