As introduced in the 1960s by the Special Tuning department, this extension allows a useful increase of fluid volume to be obtained by fitting to the neck of metal-can brake or clutch master cylinders. 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 master cylinder, and then the extension is screwed down on to it to achieve a good seal. Note that it does not fit the modern plastic-body cylinders, only the metal bean can.
For replacement o-ring see BCA4964.