Do these mount to factory roof rails or do I need aftermarket ones?

These bolt directly to your vehicle's factory roof rail system at OEM attachment points. No additional rail kit needed.

Will I need hardware to install these, or does it come with bolts?

Hardware is not included with this set — use the fasteners already present at your factory roof rail mounts or pick up standard hardware from any hardware store to spec.

Can I carry a roof box or kayak rack on top of these bars?

Yes. These cross bars are designed to handle roof-mounted accessories. Respect your vehicle's weight limits and secure cargo properly.