1994 850 front rotor size?

[panopticon]

I'm trying to get front rotors for my wife's 1994 850 non turbo, and there appears to be 2 different sizes:
11" or slightly larger...

Is there any way to know without actually removing the rotor and measuring it? Which size is more likely, if that can even be answered?

[Jot]

The smaller is what you want.

[panopticon]

many thanks sir.