Will these fit my wheel studs without modification?

These are M12 x 1.25 nuts, so they'll thread onto any stud with that specification. The 50mm length is designed for extended fitment, so measure your current nut length before ordering to confirm these won't sit too deep or proud.

Do I need to prep or paint these before installation?

They ship with the purple finish applied and ready to install. No prep work needed—hand-clean them if you want, then thread them straight onto your studs.

What happens if one nut gets damaged or stripped?

You've got 20 in the set, so you have spares on hand. If you strip a stud, that's a stud replacement issue, not a nut problem. Keep the extras for future wheel service.