well i decided to try to save a little money. instead of buying the twin air cage & filter for $100. i found that the same year yzf parts work on the wr intake. although i run a yzf airbox already this will work on the wr box also(as its still the same intake shared by both bikes) i had to order the fire resistant twinair(yz450f) and then the yz 250 2-stroke filter cage, wing bolt,& washer(don't skimp on the washer its a special one) then the cage reciever from yzf (the part that attaches to the intake) all this totaled less than $70. now i know people say " no more HP on the dyno" when removing the screen. BUT,this swap also lets alot more airflow just because of the design(the wr stuff is much more restrictive) ok well now you all say well your gonna lose bottom end! well,yes and no. i've done so much to enhance the bottom that the addition of the boyesen ap cover about made it too much. now the power comes in right off idle but is a much smoother power that builds evenly to a (now unbelievable) mid and top. this power delivery is awesome for the tight woods i ride. i call it luggable screamability ...... now that i think about it , if i would've bought the twin air cage it just would have been for the wr reciever and i would not have gotten as much airflow;just no screen !