The BSITN B8104 Bathroom Heater Duct Check Valve is designed to prevent backdraft and maintain proper ventilation in bathroom exhaust systems. Made from durable PP plastic, it ensures long-lasting performance and resistance to heat and moisture. This check valve fits 8-10cm exhaust pipes, making it compatible with most bathroom exhaust fans and heaters. Its aluminum foil design adds flexibility for installation. The BSITN B8104 effectively prevents air from flowing back into the bathroom, reducing odors and improving indoor air quality.