The RF class was built on the same underframe and with the same dimensions as the XL box car. About 2,800 were built beginning in 1906 for PRR and PL with a number of billboards. The XM class was also produced, identical to RF in appearance but without ice bunkers. A number of cars were transferred to express service under contract to Adams Express and later, American Railway Express. The cars ran for FGE as late as 1934.
Modenized kits model the cars with metal roofs and ladders.
Stripes are included in the decals where appropriate. Lettering covers the life of the car.