Hose from the PCV valve to the oil filter housing. Often called a PCV or CCV breather hose. Over time these hoses can become brittle and fail, negatively affecting your idle and fuel mileage.
Fits the Following:
2004-2006 VW New Beetle TDI
2004-2006 VW Golf TDI
2004-2005 VW Jetta TDI (not late 2005.5)