This precaution released by Hyundai warns of modifications to front seats.

Hyundai vehicles are equipped with side impact air bags installed in both the driver and passenger side front seats. Any modification of the seats may prevent proper operation of the side impact air bags when they are intended to deploy in a collision and can cause serious injury or death.

To ensure proper operation of the side impact air bags, do not install any accessory seat covers. Do not re-upholster the seat backs with aftermarket upholstery (such as a leather kit).

Do not repair damaged upholstery without using Hyundai Genuine Parts.