I emailed the ebay seller for more info, very quick response recieved.
Basically the b.box delete is with a 2.5" dia pipe which is fine with the stock exhaust.
If you want to use blueflame products in the future, then you'd need to buy a whole new CAT back system as this would be in 3" dia pipework only.
So two options. Delete pre CAT and add the b.box delete section and keep OEM exhaust,
OR
A brand new 3" shiny CAT back system!!!!!!!