This kit allows an additional amount of air volume directly to the air filter to use as a tuning tool when jetting and adding modifications.  Because the modification is to the lid, it remains washable and no damage is done to the much more expensive air box.  To install, simple trace out the area of plastic to be removed from the lid, remove the material with a drill and/or saw, then install the dual layer filter material between the lid and the supplied retainer with the supplied screws.  Lid not included.