This is a great idea and saves a lot of weight but the shifting performance is not there, whatever time I hoped to save with dropping weight was lost tenfold with poor shifting. I spent hours trying to get this working with Ultegra 12spd but I had to choose between having the high or low end of the cassette not shifting correctly, this usually points to a bent derailleur hanger but I checked it twice and it was straight. I own a Park Tool DAG-2.2 and consider myself to be a competent home mechanic. My chain (Ultegra 12spd) only had a few hundred miles on it so I highly doubt that was the issue. I may have gotten a defective one but looking at this cassette next to Shimano's it's obvious the there is far more tooth profiling done on the Shimano, while I wouldn't expect Prestacycle (or Edco?) to be able to copy it completely I would expect more effort to be put into the design so it will work better with the Shimano chain especially given how much they are charging for this cassette. Eventually I gave up and put the Ultegra cassette back on my bike and the shifting has been perfect as expected. Also considering that saving weight near the axle is far less noticeable than saving it near the rim I won't be buying this one again, I would suggest spending the extra money on the Dura Ace cassette if you really want to save weight wherever possible.