Most after market filters will flow air better than the stock OEM Filter. These filters are ideal for shimming and re-jetting modifications and may offer small performance gains. Gains of 1-2 hp and better throttle response have been gained from these. However, to get the most benefit, shimming or rejetting is recommended. Take the time to look up "Air Filters available for the 2008 & up Kawasaki Ninja 250R" on the net and check the reviews. Also for the FI Ninjas, read these... "Is another airfilter really better than OEM?" & "For those with FI bikes"