Will these bolt straight into my existing fog light openings?

Universal housings fit standard openings, but mounting tabs and hole spacing vary by vehicle. Test-fit before committing to permanent fasteners—you may need adapter brackets or custom drilling depending on your bumper design.

Do these come with wiring harnesses or relay modules?

The housings and LEDs are included. You'll need to source your own wiring, connectors, and power distribution based on whether you're running them as DRLs, fog lights, or auxiliary lighting. Refer to your vehicle's electrical schematic for proper integration points.

Can I use these as actual fog lights or just for looks?

Brightness depends on your specific LED wattage and beam angle—specs not detailed here. They work best as daytime running lights or supplemental lighting. If you need them to cut through heavy fog, compare lumen output against dedicated fog light performance specs first.