Fender liners are semi-rigid panels installed inside the wheel wells, directly behind the front and rear fenders. They shield the vehicle’s undercarriage from road debris, stone chips, and water spray, while also reducing noise, vibration, and harshness (NVH). Constructed from materials like thermoplastic, rubberized polymers, or composite blends, liners incorporate mounting points corresponding to factory locations. Some designs include integrated splash shields or accommodate aftermarket accessories like fender flares. Effective liner integrity maintains corrosion resistance within the wheel well and protects adjacent components.