The 10" and 12" Agility have slightly different mount points for the exhaust, and there's also a 16" Agility nowadays, which is a completely different beast...
The 12" is still the most common version of the Agility, but I think it's wise to look for a supplier that specifically mentions the type of Agility that the exhaust is intended for, or a supplier that is known to handle return shipments fair and quick, so you could return the exhaust for a refund if it doesn't fit - or you could just ask a few suppliers if they can tell exactly what type(s) they have in store...
BTW : I have successfully adapted a 12" exhaust for a 10" engine once, but it involved some welding - and the other way around (10" exhaust for 12" engine) would have been even more troublesome...
