A lighter Miata flywheel reduces rotating mass to provide significantly improved engine response and acceleration while reducing stress on your crankshaft and bearings. We use a lightened Miata flywheel in our own 2006 MX5 Miata and it significantly raises the fun factor! For those planning race use, or future turbo or supercharger installation, consider our heavy duty MX5 Miata ACT clutch kit to provide significantly improved clamping pressure.  Nonetheless, if doing any stop and go traffic you want to be careful about not going 'too light' on the flywheel.  And note that the lighter the flywheel, the more driveline chatter you will hear.