SoundFX™ Steel Oval Direct-Fit Aluminized Exhaust Muffler (18977) by Walker®. Optional. Muffler Inlet Diameter: 2.5″. Muffler Outlet Diameter: 2.5″. Muffler Body Length: 28″. Muffler Overall Length: 32″. Muffler Configuration: Offset – Offset. This muffler is the right choice if you opt for quality acoustics and performance. Walker offers 100% aluminized steel SoundFX™ Mufflers with direct fit and universal fit options available, both designed to maintain a quality appearance and agreeable exhaust tone.