First let me preface by saying I am not a grammar Nazi (I mess my own language up all the time--and I tutor it for Pete's sake). I fully realize many here are not native speakers and English is tough (even to native speakers). I work with students who are non-native speakers all the time. But just as I think it is wrong to belittle people for errors I also think it is wrong not to help those who want to gain a better understanding. I say all this to point out that I am not trying to put anyone down.
Any way I just want to point out that
Dual means two or a pair or something. While
Duel means a contest between two people with deadly weapons.
Again not trying to be an ass, just trying to help those who may not realize the difference between these homonyms (words which sound the same but have different meanings--of which English has a ton).
On that note, one of my favorite quotes about my native tongue:
The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don't just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary. --Jame D. Nicoll