To Clean, Use our Air Filter Cleaner and Degreaser Pre-Filter: 51901 Flange ID: 3.5" Base: 6.0" Top: 4.75" Height: 6.0" Shape: Round Volant's high performance, 5 layer oiled cotton gauze air filters are made of the highest quality textiles, pleated between a top and bottom aluminum screen. Each filter comes pre-oiled and ready for use. This design will allow the highest air flow rate possible and a very long filter life and maintenance intervals (up to 40K miles depending on driving conditions). Use Volant's two stage cleaning kit to thoroughly clean and re-oil the filter. We recommend cleaning the Air Filter only when necessary. Inspect the filter every 12,00-15,000 miles to ensure peak operation.