K&N Custom Assembly Filter Kits utilizes an adapter or tube that mounts directly to the air box. The universal clamp-on air filter then attaches to the adapter or tube. The large mounting surface of the clamp-on air filter provides better stability during rigorous riding. The assembly adapter or tube acts as a velocity stack within the air box. K&N Custom Assembly Filter Kits, like all K&N air filters, are designed to provide excellent filtration and outstanding air flow.