When buying one for myself found that there were , in fact, two slightly differing dvi cables available.
1.Single link
2.Dual link
Basically the Dual has more pins/connectors
What actual real benefit a dual link gives over a single link I never really found out and as my monitor was happy with either (and I assumed that more is better) I bought the cheapest dual link I could find (single link wasn't any cheaper) and no problems !
You might want to check which is 'better'/'appropriate' for your monitor.
N.B. I do not know if all monitors that have a dvi connection can take either link - I believe this is the case but if I am wrong would someone please correct me.