The MTH Union Pacific 4012 4-8-8-4 Big Boy Steam Engine MT-3021 LP is a detailed scale model of the iconic Union Pacific 4012 locomotive, known for its massive size and power as part of the Big Boy series. This model features precise detailing that replicates the original steam engine's design, including its unique 4-8-8-4 wheel configuration, which was instrumental in handling the steep gradients and heavy loads of the Union Pacific Railroad during the mid-20th century.