I believe the k and n filters are 2 1/4" but I'm not positive they fit on 33mm pwk carbs. I will get a measurement this afternoon. Also I still have all of the above for sale except the grill, UNI pods, and the throttle assembly. Need all of this stuff gone, sent my cases and cylinders off to redline yesterday. I'm so stoked, need to sell stuff to put towards a 4 mil crank now