Our parts are made in a jig that is constructed around an OE part. Although our parts may look different to the original they start and finish in the same place, and will fit in the same way the OE part does. Our cat units that house the monolith may be slightly smaller than the original, but they can be used on engines up to 5200cc. Our cats also have no need for pre-cats, unlike some OE parts. ALWAYS make an attempt to fit the cat to the vehicle. It may look different to the OE part, but if you have the correct cat for the vehicle it should fit. When fitting the cat fit it up loosely at the front and back before tightening it up evenly at both ends. If one end is tightened up fully before the other end is fitted the cat can be pulled out of line, and appear not to fit. If the part still won’t fit contact the technical department with details of the fitting problem and full details of the vehicle. You may have the wrong cat for your vehicle.