The filters are priced per piece. 

Specifications: 
Design: Oval
ID: 38 mm
Length: 87 mm
Outside Diameter Big: 100x75 mm
Outside Diameter Small: 75x50 mm
Flange: 16 mm
Top Style: Rubber top

The filters are also washable. Oil them in and you are ready for the road again! You can also drive through the rain when it's oiled in.