Do these lights need any modification to the roof before mounting?

Mounting method not specified — you'll want to test-fit on your roof before committing to adhesive or fasteners. Measure the 38" width against your roof clearance and decide if drilling or surface mounting works better for your vehicle.

Can I run these lights off the factory electrical system, or do I need a separate relay?

The kit includes a wiring harness and rocker switch, so you can tap into your existing electrical system directly. Most roof light installs run to the battery or fuse block for independent control — check your vehicle's wiring diagram to find the cleanest tap point.

What if one bulb burns out after purchase?

Return process specifics are handled through ModSupply's standard return policy — contact support with your order number and they'll walk you through the next step. H3 bulbs are a standard size, so replacements are cheap and available everywhere if you need them fast.