Not to confuse you even further John, bit it bears mentioning. The Bachmann Mallet is an inside frame locomotive, so what Greg and Semper said regarding it is true. However, on outside frame locomotives, like the K-27 for example, the counterweights are not "the "half moon" part of a driver, the filled in part." The drivers on such a loco are inside the frame, but the counterweights are on the outside connected to the axle ends. I only bring this up here because discussions of Bachmann's previous loco, the K-27, revolved around "loose counterweights."