Need help with cat/de cat size for civic saloon sir

[JDM-JOE]

Well lads fairly new to the ins and outs of Hondas basically my sister is driving a 97 Si ferio sir saloon the exhaust system from the cat back was fairly rotten so she got a 2nd buddy club from a lad that owned a 99 facelift ferio.

Put it on the car but it's to short it's about 3-4 inches to short to meet the cat I measured the catalyst on her car and it's 12in so would I be right in saying that there is a 12in and 16in cat? And could you tell me what size diameter they are is a sir cat and manifold 2.25 in diameter ? Thanks

 

[B18C'R EK]

if the exhaust is too short then you need adjustable decat to sort the problem out

 

[JDM-JOE]

Oh I no that but I need a cat for nct/mot I'm just thinking maybe did I buy a teg cat back, your man maybe telling lies?