The c1 chainring for powermeter from powertap is a full featured crank based power meter that features dual sided measurement manufactured by fsa the one piece chainring design provides added stiffness for shifting no matter the terrain available in 5339 5236 or 5036 chainring tooth options for 5 bolt 110 bcd cranks the c1 mounts to existing hardware on the bike it uses dual band ant and bluetooth smart connectivity making the c1 an obvious choice for riders looking for more features