A multi layer cotton and silicon based air filter element designed to fit perfectly in the iconic BMW kidney grill and Osprey V4 front mount intake, as with all Osprey filters, these can last for years if cleaned correctly although they are cheap enough to replace at regular intervals too. 
 
Measuring 235mm x 130mm with a 90mm intake neck and 190mm filter element. These may work on other applications but are purposely designed and made for the Osprey V4 front mount intakes for 1 and 2 series B58 cars.