Will these work on my factory wheels or only aftermarket?

Acorn lug nuts fit both factory and aftermarket wheels. The tapered shape is universal — just confirm your wheel holes accept M12 x 1.5 studs before ordering.

Do I need to worry about these coming loose?

These are lug nuts only — they depend on proper torque to your vehicle's specification, which you'll find in your owner's manual or service guide. Retorque wheels after your first 50 miles after any installation.

Can I use these if I have open-end lug nuts now?

Yes. The M12 x 1.5 thread matches most applications. The closed-end design means you're swapping from open to sealed — just verify your current thread size and pitch before you buy.