A useful increase of the fluid volume can be obtained by fitting this extension to the neck of metal-can brake or clutch master cylinders. Note that it does not fit the modern plastic-body cylinders, only the original bean can. This idea was introduced in the 1960s by the Special Tuning department. It is translucent to allow easy viewing of the fluid level, ideal for race cars. Includes o-ring, which is fitted first on the threaded neck of the metal master cylinder and then the extension is screwed down on to it to achieve a good seal.
For replacement o-ring see BCA4964.