Xeon x5355 processors models that fits 2006 pro 1.1

I'm about to get 2 of these guys, but i am confused about why there are different models with the same name.

many sell x5355 but they are called SLAEG, some others call them with another sequence of letters (SL9YM) , while buy.com says that it is a single core processor.....guess they just had too many drinks while writing the specs 🙂

Which one is the right one for the mac pro 1.1? And is suggested to get them new or used are fine?

Thanks!