36" smooth back wheels Accurate markings True to prototype Smooth tracking Free rolling Contoured Insulated Axes RP-25 Free rolling wheels Non-magnetic Metal wheels.Smooth wheelsets are most commonly found on all diesel era rolling stock.Kadee?? wheel sets are manufactured to the most exacting standards and feature: RP-25 contour, non-magnetic metal wheels and insulated needlepoint axles.KadeePart KAD522