This set is designed for the Hotchkiss (based) kits of Bronco (1:35). If you do not want or need new bogies, this sets will give you just new road wheels, new sprockets and idlers wheels as well as return rollers and a spare road wheel. Finally a late engine hatch is included. (Assembly) instructions can be found here: http://www.shapeways.com/forum/index.php?t=msg&th=10945