XPOWER-S POWER METER SPIDER XPOWER-Sis a reliable and stable spider based power meter that is easy to use and install. Based on the excellent structural mechanics and electronic circuit design you can get 1.5% accurate measurement of watts in every second. Up to 17 models XPOWER-S can compatible with 9, 10, 11 or 12 speed drivetrains. Road, mountain, triathlon or track.