K&N offers drop-in replacement air filters for the 90-97 NA, and the 99-05 NB Miata (including the Mazdaspeed). These drop-in K&N filters are designed to increase the horsepower and acceleration of your Mazda Miata while providing excellent filtration and retaining the OEM filter box. K&N filters are custom designed to fit into your existing factory air box for simple, fast installation. Stock replacement K&N drop-in air filters for Miatas are covered by a Million-Mile Limited Warranty. K&N Filters use oil to assist in filtration, and can be washed and recharged using the K&N cleaning kit (sold separately).