Boyesen 604 Power Reed For: Yamaha Tri-Z 250 all models; Yamaha YZ125 1998-1992 Power reeds use a patented dual stage fiberglass design for more air flow, more air velocity and more power 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 Longer overall life: Boyesen power reeds outlast all other aftermarket reed petals Minor change gives major horsepower improvements and fuel economy