Eisenmann M3/M4 Performance ExhaustEisenmann F8X M3 M4 Rear muffler (valved) 4x90mm Each system is constructed from high grade 304 stainless steel, with a specific attention to wall thickness throughout to create the best combination of fantastic sound and reduced weight. The canisters are machine pressed into a shape specifically designed for the F8x M cars using a series of deep draw dies, resulting in extremely high canister rigidity and contributing to Eisenmanns signature tone.