Tapered cone air filter that fits Dellorto PHBH 26-30mm carbs. These clamp on filters fit great and use wire mesh and not a paper element like a K&N. filters are 3" at the carb end and taper down to 2" with a nice chrome end cap. Overall length is 3" and work great on 125-450cc single cylinder bikes. The ID of filter mounting flange is 42mm.