Fits the following Mini Cooper non-S models:

2002-2006 R50 MINI Cooper Hatchback 
2005-2008 R52 MINI Cooper Convertible

For the Cooper Belt Tensioner Tool, see NME5992.

MINI Factory Replacement Belt Tensioner Assembly for the Cooper S.

Fits the following Mini Cooper S models:

2002-2006 R53 MINI Cooper S Hatchback
2005-2008 R52 MINI Cooper S Convertible

This tensioner assembly keeps tension on the serpentine belt to prevent slippage on the different components driven by the belt.

For the Cooper S Belt Tensioner Tool, see NME5990.