Originally Posted by AdelaaR

It's a 9-speed cassette so it will work with most 9-speed derailleurs like the deore you speak of and definately not with 8-speeds.
On a 7.3FX I would not recommend you to get an ultegra cassette though, as it would mean that your cassette would by far be your most superior part and there is no point in that ... in that case you could easily settle for a "tiagra" cassette and save yourself half the price or more ... your choice ofcourse
I have an XT rear derailleur and so I chose the quality of cassette that goes with it, being the ultegra.