Filterskins are an extremely thin but durable air filter cover. While allowing maximum airflow, an oiled Filterskin will catch 90% of the dirt that tries to pass through the air filter. Between races or between rides, simply pulling off a dirty Filterskin and sliding on a clean one can save you time and actually save money on expensive solvents and oils. Filterskins are extremely elastic and each size will expand over a wide range of air filter sizes. Note: For the best protection and easier air filter maintenance, it is recommended that you use a FLO Air Filter and Pro-Seal Air Filter Gasket (both sold separately).