These two are not models, but I am posting them to show you the exteme in the Hobby of Pinewood derby racing. These are the Super Pro Mods or Unlimited cars. They have two flanged minature bearings per wheel. Mine I only run the bearings on the rear wheels and use a .022 diameter needle axle on the DFW. The initials stand for Dominant Front Wheel. This wheel is used to gently steer the front end of the car into the rail thus keeping the two rear drive wheels off the rail so speed is not scrubbed off. The straighter the car runs the faster the time. I know it sounds crazy, but this is how it's done. Wheels weigh .8 grams without bearings and are made from acrylic. A good bearing car will travel the 42' in 2.8 seconds and some change. A door slammer will run around 2.954.......that is the current record held by me. Hope this explains somewhat how this PWD thing works.