Do these plug into the factory wiring, or do I need to run new harnesses?

They use the factory electrical connectors and switch. If your vehicle has OEM fog light wiring already in place, these connect directly. If not, you'll need to tap into or add a relay circuit.

Will these fit in the same slots as the original fog lights?

Yes — they mount at the factory fog light points with no drilling or bracket modification needed.

What's the return process if these don't fit when they arrive?

Test-fit them before closing up the bumper area. Contact ModSupply within 30 days of delivery with photos if there's a fitment issue — we'll work out a solution or process a return.