The bridge of the Wildcat moderators is the part with thread, to suit whatever thread type the rifle barrel has. Calibre is irrelvent to this part.
Pic below (used from UK custom shops website) to demonstrate what a Wildcat Predator bridge looks like.
One of the other main parts is the diffuser, which others may refer to as the baffle. The diffusers are colour coded and have a bore size appropriate for the calibre.
The remaining parts are inner and outer tubes and bush's.
Parts for Wildcat Predator Moderators and Wildcat Evolution moderators are different and are not interchangable.