Small rear weight box bolts to the lower 2 bolts that holds the axle housings on. This box is precision laser cut out of heavy 10 gauge steel and welded together. Small box size measures 10" wide x 9" long and is about 5" deep. Box has a removable rear cover to load weights in an out of at the track. This box is a fully welded piece. If you would like to save some money and weld your own together the parts only are available in the drop down options box.