The MTH 20-20005-1 Union Pacific 3GS21B "Genset" Diesel is a 1:48 scale model of a diesel locomotive designed for O gauge model railroads. This ready-to-go pre-built locomotive features a digital control system, smoke unit, light function, MTH DCS, and sound function. Made of plastic in a vibrant yellow color, this Union Pacific Railroad-themed locomotive is perfect for model railroading enthusiasts looking to add a realistic touch to their collection. With its high grade of C-9 Factory New-Brand New, this locomotive is sure to provide hours of enjoyment for both children and collectors alike.