diesel centre pipe for MK1 VRS

Hi I hope someone can help. I recently got a blueflame sportcat and downpipe 2.5"....

Obviously this will not fit the standard centre section on a MK1 octavia VRS so was looking at a diesel non-res centre sectionwhich is flared at the cat end but does anybody know the size of the flared bit???

Would like to fit myself plus dont want to weld bits incase I return to standard at anytime

Paul