the only way they fit? the arches are held on with self tappers(and screws in some cases) and then the sill extensions stick to the existing sill with the mounting kit, and thats it really, because of my small bumpers i had to alter the very front parts of the door trims as they were abit too long and needed to fit flush, and then theres the front spolier which i had to cut up quite abit and then tie string to the ends and then under and up the engine bay abit to hold them flush to the arches, masive bodge job but you cant really tell now its done,