I purchased this chain as a spare to sit on the shelf for the original on my CX bike. That chain has almost 3000 miles of Nebraska gravel, CX, and MTB singletrack and is in great shape with little wear so far. Like I said, tougher than nails. Paired with the SRAM X-Sync it makes a near bombproof system. Of course, I keep it cleaned and lubed well, but, man, it's a tough chain.
This is the lightest and quietest Freewheel cassette I have used. I own two of these. The first one has 14,000 miles on it and looks and performs like a new cassette, I bought a second one to go on a new set of wheels. It was significantly cheaper than the first one was. A much easier purchase. I use it with eTap, but I am told that it works quite well with Dura Ace or Ultegra.
Decided to install this on my bike before a Gran Fondo just in case I needed an extra gear while climbing in the 4,500 ft elevation range. Glad I did as it helped towards the end of the ride when there was one last hill to climb at mile 95. Not only was the extra gearing great, but the new cassette was awesome with regards to shifting throughout the whole ride. Western Bikeworks had what I needed in stock and I was able to swing by and pick it up same day.