Allows replacement of stock reed stop with a Rev-Plate which permits the reeds to open freely and function efficiently. The top reed is lightweight and resilient for crisp throttle response at partial throttle or low RPMs. The stiffer, bottom reed is ported to provide maximum flow and horsepower at higher RPMs. Dual-stage design incorporates a specially shaped top reed and a ported bottom reed. Increases horsepower for less money.