Will this mirror stay stable at highway speeds while towing?

Yes. The OEM-style profile is designed to match factory aerodynamics and won't introduce vibration or flapping at speed. It bolts to existing factory mounting points for solid, rattle-free attachment.

Does the heated element require a separate switch or relay?

The heating function integrates into the mirror assembly. Your truck's existing rear-window defroster circuit typically controls it — no additional wiring or installation complexity.

What hardware comes with this mirror?

Mirror assembly only. Mounting hardware is not included — you'll reuse the fasteners from your original mirror or source replacements to match your truck's factory specification.