USAT 40 foot PS-1 box car This box car is the "ultimate" series, highly detailed, metal wheels. The box cars come with a mounting pad for Kadee couplers, the models with the prototypical "slack action". Kadee 830 for the original style coupler, and Kadee 906 for the new "Type E" prototype coupler. These and the AML 1:29 box cars are my favorites, finer detail than the Aristo, coupler lift bars, come with metal wheels, and the thing I seem to notice most, the scale door latch (the Aristo one is an enormous clasp befitting costume jewelery). When installing the kadees, usually I can reach inside the car to place the nut on the machine screws to secure the coupler box. If this is difficult, then remove the screws that hold the root and shell together.