The unifilters in the pic above work very well. Bit messy to maintain.They fit over the stock velocity stack and are fastened with a reusable cable tie. They are cheap. I carry them and the RAMAIR for those who want filters under the bearclaw. America must be the land of clean. There is no fu$king way in hell I would send a customers bike out on THE STREET without a filter. Drag racing why not, 600 passes is under two hours engine time and about five years racing about here. On the road, motor would be screwed in no time. I remember when the ZX12R kawasakis first came out, their little open foam style panel filters would let the dirt in thru. 15000kms and the back of the inlet valves were like shot blasted and the motors fumy. We would put new K&N's in straight away to stop that. Bottom line is do what you want to your own bike, as you're the guy picking up the bill.