(11761711717)(18111245429) - Exhaust Downpipe Flange Gasket (3-bolt)(Elring/40mm bore) -Bavaria/3.0Si, E30, E12/E28, E23/E24, E31 (4 available)

The BMW part number 18111245429 fits the exhaust downpipe-to-manifold flanges on classic BMW engines from the late 1960s through the early 2000s, including the M20, M30, M70, and M73.  The part number has been superceded to the current 11761711717. This "metallic" gasket is manufactured by ElringKlinger AG, a premier German automotive supplier specializing in high-performance sealing systems and gaskets. You can confirm this by looking closely at the bottom-right corner of the gasket in your photo, where the distinctive oval "Elring" logo is stamped directly into the metal surface. It stands out from standard automotive triangular exhaust gaskets due to several distinct engineering characteristics: 

• 40mm Internal Bore Diameter: It features a precise 40mm center opening tailored strictly to old-school BMW factory downpipe routing. 
• Integrated Fire-Ring (Crush-Zone): The central hole is surrounded by a raised, reinforced metal fire-ring lip. When torqued down, this ring compresses permanently into the flange gap to contain highly pressurized exhaust gases and prevent blowouts.
• Tension-Retaining Locking Ears: Next to each of the three bolt holes, you will see a semi-circular curved indentation stamping (locking tension tab). These serve as integrated lock-washer tabs that flex against the flange surface under load. They prevent vibration from backing off the copper exhaust nuts over time without needing standalone lock washers.

BMW 3-Series (E30 Chassis)

• 1984–1987 325e / 325es (2.7L M20)
• 1986–1988 325 Base (2.7L M20)
• 1987–1993 325i / 325is (2.5L M20)
• 1988–1991 325ix (AWD, 2.5L M20) 

BMW 5-Series (E12, E28, & E34 Chassis)

• 1975–1978 530i (E12, 3.0L M30)
• 1977–1981 528i (E12, 2.8L M30)
• 1982–1988 528e (E28, 2.7L M20)
• 1983–1984 533i (E28, 3.2L M30)
• 1985–1988 535i (E28, 3.5L M30)
• 1988 535is (E28, 3.5L M30)
• 1989–1990 525i (Early E34, 2.5L M20 — Requires 2 gaskets) 

BMW 6-Series & 7-Series (E24, E23, & E32 Chassis)

• 1977–1978 630CSi (E24, 3.0L M30)
• 1978–1984 633CSi (E24, 3.2L M30)
• 1985–1989 635CSi (E24, 3.5L M30)
• 1978–1984 733i (E23, 3.2L M30)
• 1985–1986 735i (E23, 3.5L M30)
• 1987–1992 735i (E32, 3.5L M30)
• 1988–1994 750iL (E32, 5.0L M70 V12 — Requires 2 gaskets)

BMW 8-Series (E31 Chassis)

• 1991–1994 850i / 850Ci (5.0L M70 V12 — Requires 2 gaskets)
• 1994–1997 850CSi (5.6L S70 V12 — Requires 2 gaskets) 

BMW Vintage / Classic Platforms (E3 Chassis)

• 1972–1974 Bavaria (2.8L or 3.0L M30)
• 1975–1976 3.0Si (3.0L M30)