Add an extra layer of protection to your catch can set - up with the Mishimoto Performance One - Way Check Valve. The diameter valve allows for ample airflow through the system, while protecting vital components from unwanted pressure. The anodized aluminum housing ensures durability of the check valve, and the Viton diaphragm and seals provide superior chemical resistance. Our Check valves are not only fully serviceable, but also covered under the Mishimoto Lifetime Warranty for a worry - free installation.