? Union Pacific's Big Boy 4014 Steam Locomotive with Train Track Building Kit and Engineering Toy Compatible with Lego for Train Enthusiasts Lovers?This advanced building set offers a delightful, immersive DIY project for LEGO fan or any Locomotives fan. All parts are compatible with Lego pieces! Offers ingenuity and endless train play.?Guarantee: We offer refund if you are not happy with your purchase. Three tests are carried out to ensure every piece of our product is entirely picked up by machine. If your sets still have missing pieces, please contact us and we will send them to you for free.The American Big Boys are some of the longest and largest steam locomotives ever built anywhere in the world. During the late thirties Union Pacific often used auxiliary engines to haul trains from Ogden, Utah up a steep pass to Wasatch. U.P. wished to simplify this system and instructed their own development department to design a new locomotive capable of hauling a 3,600 ton train (max 4,200 tons) up the steep pass.