Airtec Motorsport 70mm Decat Downpipe Exhaust Pipe Ford Focus RS MK3 16-18The Original Catalyst and down pipe , unlike the older ST225 and Focus RS MK2, are made in one piece. This new design features some restrictive bends and an exit bore size of only 55mm. With a new bore size of 70mm the new AS performance Replacement Down Pipe has over 50% more capacity. This part is sold for motorsport and off road use only and will NOT be able to pass a UK MOT emissions test or police road side checks.