54MM Cylinder Filter Rubber Top RO-5405. 

Specifications:

• Part Number: RO-5405-100 / RO-5405-127
• Design: Round
• ID: 54 mm
• Length: 130 mm / 155mm
• Outside Diameter Big: 90 mm
• Outside Diameter Small: 90 mm
• Flange: 25 mm
• Top Style: Rubber top

The filter is washable. Re-oil it and you're on your way again.

The oil ensures that you can keep riding in the rain.