This is a pig themed derby car body I made for with my oldest daughter. The opening in the middle will hold a lego character. In this case a Lego Friends. You will have to let you kid paint it to get such a nice look.There are 2 versions the regular has all 4 tires at an equal height, the "lifted tire" version has one of the front tires .100" higher than the others. The theory there is less rotational inertia, will allow the car to go faster. There are 2 holes that run about 2/3 the length in the back, I added steel rods in there to get my mass up and have my center of mass closer to the back wheels. I printed is only about 15-20% infill. This made it way under our weight limit and then I added the weight where I wanted it. The tail is 22 AWG solid core wire. I just drilled a hole and hot glued it in.