An oil cooler will help keep your engine running cooler. A 13-row cooler was standard on the Cooper S; this 16-row cooler is recommended for race/performance applications. UK-made, with standard .50" BSP fittings. Made in the UK by Mocal. Don't install this on a road car, it will over-cool the oil and reduce its effectiveness.
For the same cooler with AN fittings as preferred by many racers, see SCO0003AN.