The Borla XR-1 Multi-Core racing muffler is a universal, high-performance muffler with a compact size that is perfect for applications with limited space and can be used on a wide range of vehicles. It uses Borla's patented Multi-Core 4-tube internal design, which flows better than straight tubing for maximum flow, horsepower and torque, and is recommended for high horsepower applications. The reversible design adds installation flexibility. It is built from T-304 stainless steel with 100 percent welded construction and a high-temperature continuous-filament fiber acoustic packing for sound control. The natural mill finish can be brushed or polished prior to installation, and there is no Borla logo embossment on this part. Borla exhaust products are handmade in the USA.
Specifications:
- System type: Universal racing muffler, reversible
- Core: Patented Multi-Core 4-tube design
- Inlet: 3 in center
- Outlet: 3 in center
- Body: 4.25 in x 7.88 in oval x 12 in long
- Overall length: 17 in
- Material: T-304 stainless steel
- Construction: 100 percent welded
- Acoustic material: High-temperature continuous-filament fiber
- Made in the USA
- Part number: 400372
FAQ
Will this muffler fit my vehicle?
It is a universal muffler, not vehicle-specific. Its compact size suits installations with limited space and can be welded or clamped into a wide range of applications. Confirm the inlet and outlet sizing and available space match the application.
Is this muffler street legal or emissions compliant?
As a universal exhaust component it carries no standalone emissions certification. Emissions legality depends on the complete exhaust system and how it is configured on the vehicle and in the state where it is registered.
What is the Multi-Core design?
It is Borla's patented straight-through, multi-tube core. The Multi-Core section flows better than straight tubing for maximum flow, horsepower and torque, and is recommended for high horsepower applications.
Can it be installed in either direction?
Yes. The reversible design allows the muffler to be installed in either orientation. There is no Borla logo embossment on this part.
What is it made from and where?
It is built from T-304 stainless steel with 100 percent welded construction and is handmade in the USA.

