This billet flywheel is very light at 4.7lbs. ARC flywheels use a Neodymium (rare earth) magnet which is the most powerful magnet on the market. Non-adjustable hub. Use flywheel key to adjust timing. Flywheel does not come with a ring gear. Without the ring gear, you will either have to use a handheld starter, or install the starter cup to be used with the pull starter. Uses stock Honda coil. No need for coil bracket and aftermarket coil. Just bolt-on and go! Very high quality. Must have item for any serious GX340 or GX390.