The mainstream material is flame-retardant PA66 (Nylon 66) engineering plastic. Some low-cost models may use PVC.
- PA66: Temperature resistance -40°C to 125°C, inherently flame-retardant, impact-resistant, and corrosion-resistant. It is a standard component in automotive parts.
- PVC: Lower cost, but its temperature resistance and flame retardancy are inferior to PA66; generally used in ordinary applications.