Our 33-inch SEMI-SCALE 0.088" width tread wheelsets with back contour are insulated and blackened. They are precision CNC-machined brass wheelsets that can be used universally with our trucks and others. The axle length is 1.005". Use them as replacements to get a very prototypical tread and contour in all types of cars. The next step in high fidelity for prototypical looks and operations.