Because a patented bolt secure system, at which two differnt riffled washers pressing out of itself, you getting tighten turbochargers and exhaust systems finally. The TurboZentrum Berlin delivers the high quality version in stainless steel for M8 and M10 threads in 2 different wides. On request you get other sizes and materials (mild steel and inconel) from stocking.
Details at www.turbozentrum.de