Just part way through fitting a new offside lower (rear) arm on the front suspension due to a clonking balljoint and weak bush. The new one is a Febi and near identical to the old one in all respects. The Febi arm came as a kit with new mounting bolt and washers/nut. The old bolt was quite standard and could only enable the arm at the inner bush end to be mounted in the centre of the elongated hole in the bush. The bolt is held centrally by some "fins" inside the bush. The new arm is exactly the same with the elongated hole and centralising fins. However the bolt it came with has two grooves machined along its length that enable it to engage with the fins and set the bush about 0.5mm in or out from the central position. I will fit the arm centrally as the old one but wonder when you would ever need to change the effective arm length with this new bolt?