Will these work with my factory wheels?

M12x1.5 is a universal fitment, but your vehicle's center bore and wheel design determine compatibility. Check your wheel's lugnut seat style matches these open-end nuts before purchasing.

Do I need to replace all 20 at once or can I buy just a few?

You can use as many as you need, but it's safest to keep a full matching set. If you're only doing four or five wheels, you'll have spares for future repairs or wheel swaps.

What's the torque spec for these?

Refer to your vehicle's service manual for the correct torque specification. Aluminum nuts can seize if over-tightened, so follow your OEM specs and re-check after your first few miles.