Buttery smooth difference between Ultegra and DuraAce - do you need it - yes! )
What can you say, this works flawlessly and is simply the best available. So if you want the best no other option, but it's not cheap. Make sure you change your chain on time so that you don't chew up the cassette quicker than you should. I got over 10,000 miles out of my last cassette with about 3 or 4 new chains during that time.
I have nothing bad to say about this product
