As long as your rear hub is a 7850 and not a 7800, which only takes Dura-Ace cassettes, then the Ultegra cassette is a good way to go. Just remove the cassette to find out-if the freehub body is TI (light grey as opposed to the Aluminum used on the 7800) you have a 7850. And as long as the chain is 10 speed it will work but some shift smoother. (Just avoid SRAM chains.) Ultrega, Dura-Ace, or Wipperman for me- and I prefer the Wipperman.

I use Dura Ace (7700) with Ultregra 10 speed shifters and cassette and 10 spd chain; it's been on several bikes and it's been bullet proof.