All components require welding, professional installation is highly recommended.
Components come from several manufacturers, all are made in the USA (except the strut tower plates made by BMW.)
Important Note: The rear trailing arm pockets on the E46 do not suffer the same type of failure that E36s are known for, as the pocket itself and mounting bosses are stronger. However, the new weak point is the factory spot welds attaching the pocket to the chassis, they can deform and eventually fail. The solution is to simply stitch weld around the perimeter of the pocket to the chassis. This is easily done the same time as doing your rear subframe reinforcements. The most difficult step is cleaning out the seam sealer and coatings to achieve a clean weld.