This balloon cart comes with everything you need to use it, save for a balloon and the dowels to be used as axles (1/4 inch dowels will fit). One wheel goes in the front, while another 2 go in the back. Additionally, there's a slot in the back of the cart to slide in one of two interchangeable nozzles. The nozzle not in use can be taped to the top of the cart to help support the balloon, as is shown in the images.
Included are all the files necessary, however you will need to print multiple wheels. While it was found that 2 large wheels in the back and one small one in the front worked best, any wheel can be inserted into any slot.