Lots of good ideas here, thank you. My magnet came with the sticky back, but it didn't stick and even near the pedal end, it was too recessed to be read. I have read about the rare earth magnet and that would be a consideration as well and as several pointed out, it would look better without the zip tie. I have also thought about some kind of putty or something to fill the hollow before attaching the cadence magnet. What I was wondering about that, is if I would also need to put putty in the corresponding spot on the other crank, so as not to create some kind of imbalance that would cause wear and tear? (I'm kind of thinking like when wheels are out of balance - perhaps I am overthinking this.)