Can I weld this directly into my exhaust system?

Yes. Mild steel tubing is designed for welding. If you're slip-fitting instead, the flared ends provide a seal without additional clamps, though you can add them for extra security.

Do I need to paint or coat this before installation?

Mild steel will rust if exposed to moisture and salt. Coat it with high-temp exhaust paint or ceramic coating before or after install to extend life. Raw steel will develop patina but isn't a failure—your call.

Will this fit my stock exhaust diameter?

This piece transitions between 2" and 2.15" pipe. Measure your current exhaust inlet and outlet diameters before ordering to confirm fit. If both sides are the same diameter, you'll need a different component.