To reach your maximum potential as a cyclist, it's a great idea to train with a power meter, and the Quarq RIKEN brings together excellent accuracy and performance in a wireless, crank-based unit. It uses ANT+ wireless technology to pair with a head unit of your choice (sold separately), to display and record your ride data. Plus, an LED indicator lets you know you've correctly synced the RIKEN with your head unit. And, the user-replaceable battery is a simple to swap and readily available CR2032. With the RIKEN's excellent accuracy you get extremely useful data, even if you swap chainrings, thanks to Quarq's Omnical technology. Plus, the SRAM-made carbon crankarms and 5-bolt precision-shifting chainrings will leave you floored by their unreal stiffness and beauty.