FSA’s Road PowerBox Crankset employs a P2M convertible spider design for multiple chainring options. FSA's alloy arms and BB386EVO spindle mated together produce a very lightweight, extremely versatile power meter crankset available with a double chainring configuration. BB386EVO 30mm AL 7050 alloy spindle fits every frame (purchase BB separately) Spider-based power sensors provide total power output measurement of both legs, with Left & Right leg output analysis available with system upgrade Bluetooth connectivity available with system upgrade Please call for other crank length / chain ring configurations