A known weak point on many BMWs, after years of being exposed to high temperatures the head of the plastic bleeder screw can easily snap off (often when installing one on a brand-new expansion tank!). With the high failure rate of bleed screws, we recognise that the market has been flooded with low quality alternatives, which is why we choose to only stock high quality bleed screws from Germany's Febi-Bilstein. Complete with o-ring.