Flow INPOWER left-hand crank arm
If you already have a Rotor Flow crank, with or without the MAS spider, you can add power to your life by picking up this INpower Flow left crank arm. As the power meter is embedded in the 30mm thru-axle, which is attached to the left crank, all you need to do is pull your existing left arm and spindle, and install this.
INpower refers to the system Rotor utilizes for measuring power. They’ve put the strain gauges and the hardware inside their Universal Bottom Bracket (UBB) thru-axle. Inside the bb=INpower. A 30mm hollow aluminum axle isn’t only strong and light: it’s got room for electronics. There are two strain gauges embedded inside the spindle. They’re powered by a single AA battery, which lasts for up to 300 hours of riding. The signal is sent via the ANT+ protocol from a transmitter on top of the left crankarm to any ANT+ enabled head unit. Stashing the electronics inside the axle does several good things. It is protected from the elements. It is protected from crashes. It puts the added weight, which is 30g here, inside the smallest possible circle: the added mass is rotating in the smallest circle possible. It is about as waterproof as a powermeter can get. And it makes the unit less temperature-sensitive: in fact, along with the programming, temperature should not affect INpower at all.