This a Genuine BMW Motorsport part made specifically for race engines. Not recommended for street use.
BMW Part Number: 11531417215
Direct replacement for 11531318274 (80C stock thermostat)
Fits all years of E46 M3, 2001-2002 MZ3 S54, and Z4M. Also Fits Euro-spec S50B30 and S50B32 E36 M3 engines – will NOT work in US-spec E36 engines.