Hi ! Trying to understand which to order, xj 99 , probably 8/99. Cant take off caliper right now, is it possbile to determine if i have full cast or composite ?

https://www.rockauto.com/en/moreinfo...1636&jsn=10106 will it fit ??

thanks for any help

 

 

Apologies for the stupid question, but what's a composite rotor? Aren't they just cast iron?