The Invidia N1 system for the Civic Si features 70mm piping and an attractive 101mm titanium tip. Made entirely from mirror polished stainless steel, all Invidia exhaust systems include their signature thick CNC flanges and precision robotic TIG welds. All mandrel bends and their signature N1 syle free flowing muffler release more ponies to the pavement for performance you will hear and feel. The N1 features and extremely aggressive exhaust note and is not for the faint of heart. If you have to ask how loud it is, it's too loud for you!