Relaxweex 3" Inlet/Outlet Straight-Through Exhaust Resonators (Pair)

The straight-through design is the key differentiator here. Unlike traditional chambered mufflers that use baffles to physically slow and redirect exhaust gases, these resonators use tuned internal geometry to cancel specific sound frequencies — particularly the mid-range drone that plagues highway cruising on modified cars — while leaving exhaust flow largely unrestricted. The result is a smoother, less fatiguing exhaust note without a measurable hit to power or throttle response.

Fitment is refreshingly simple: 3" inlet ID, 3" outlet ID, 13.8" overall length, and a 4" round body diameter. That spec lines up cleanly with the vast majority of 3-inch cat-back and axle-back exhaust systems common on turbocharged BMW platforms. The compact body diameter also keeps clearance issues to a minimum, even on cars with tighter undercarriage packaging. Note that these are slip-fit resonators — confirm your exhaust system uses clamp or weld connections before ordering.

Sold as a pair, these work best installed symmetrically on dual-exit exhaust setups, though a single unit can also tame a particularly resonant section of a mid-pipe. For BMW owners running an aggressive aftermarket exhaust who just want to take the edge off without swapping to a full muffler, this pair delivers practical, durable results without overcomplicated installation or an outsized price tag.