K&N Universal X-Stream Clamp-On Round Air Filter 3.531in Flg ID/4in OD/5.969in HK&N XStream Top Universal Air Filters take performance to the next level with the addition of a filter within the filter's top adding more filter area for higher air flow and a longer service interval. The XStream Air Filter provides awesome air flow and outstanding filtration. When racing, in any environment, racers need all the protection and airflow they can get. K&N delivers. All K&N universal air filters are constructed with ultra strong molded