I need to replace mine. I noticed on the FCP site they list 2 different ones.

One is for car with 11 inch rotors other if for car with 12 inch.

I own a 99 T5 so I assume I have the 12 inch rotors yes? is there another way to make sure to get the right one if I dont get it from them?

 

OK, this concept is from my wife, who doesn't know a T45 screwdriver from a torque wrench. But, if it involves buying something - anything - she's an absolute pro.
Now, we have all torn something down and then realized that we had the wrong parts so I understand your concern.
So, buy them both, send back the one that doesn't fit. She of course does this with clothes, shoes, purses, etc. (She normally is a size 6, but has been known to buy a size 4, 6, and 8 so if she gains or loses a few pounds she can still wear something she really likes!)
Works every time, and the few minutes it will take to ship back the incorrect one will more than be compensated for by the time saving of getting the wrong one if you only order one and guess wrong. Don't assume that the T5 automatically has the larger rotors, or that your rotor/mount matchup is correct. I did a similar thing with brake pads once once. Got the wrong ones. And recently discovered that I had

 

LOL, sounds to much like "sport" to me.

You can pull the wheel and look at that thing. I didn't know the '99's had different sizes but I know the earlier 850's sure did. Here is my DIY instructions on it.

Motor mount, right side, Volvo S70, replacement instructions