Basic leaf spring suspension for RC trailers. The width is set by using a 5mm threaded rod and locknuts. There should be about 8mm of travel with the last couple mm be extra stiff. The bearing size is 5x11x4. Most of the hardware is m3x14mm and m3x8mm. This was designed to use touring car size tires although other sizes will likely work. You can use these parts for 2 or more axles with no limit. 4 springs total seems to be enough to support the trailer and 2 RC cars.