This genuine plastic cap is the exact replacement for the single line brake cylinders pre-1976 and all clutch masters. While it doesn't commonly break or wear out, it is often lost or can become discolored over time, making it necessary to replace. This white plastic cap is an upgrade from the early steel master cylinder reservoir caps which had a tendency to rust. In addition to fitting single line brake cylinders and clutch masters, this cap also fits Midget and Sprite models as well as the MGB from 1963-1967. Keep your car's braking and clutch system in top shape with this high-quality plastic cap.