Nobody pays much attention to the piston rod seal in their brake master cylinder until it leaks. Even when it does leak it won't cause much more than carpet damage, unless you ignore it. When the OEM piston rod O-ring does need replacing due to wear causing leakage, that's the time to fix it once and for all. Like all Marsh Brothers products, our glands and seals are developed to last for the long haul. For more information about our Brake Master Cylinder Seal kit, please contact us at [email protected] www.MarshBrothersAviation.com