catalyst assembly 10 terminates in an angle relative to an axial direction of the underfloor catalyst assembly 10 when assembled the exhaust pipe 200 and the underfloor catalyst assembly 10 meet at their respective angled portions and the pipe and catalyst assembly are coupled together in use by coupling the exhaust pipe 200 and underfloor catalyst assembly 10 together at the angle space is saved such that the underfloor catalyst assembly 10 can be moved further forward with respect to the vehicle and the underfloor catalyst assembly 10 can be heated quickly for more efficient operation it will be appreciated by one of ordinary skill in the art that the rearward end 160 of the exhaust pipe 200 and the forward end 165 of the underfloor catalyst assembly 10 can include a coupling or other suitable mechanism for mutual attachment according to another embodiment the underfloor catalyst assembly includes a compact structured flange which allows a working tool easy access site from the side of the catalyst assembly when the flange of the catalyst assembly is coupled to the exhaust pipe the compact structured flange further enables the catalyst assembly to be mounted close up to the engine so that the catalyst rapidly reaches a light off temperature in addition the catalyst assembly comprises a catalyst carrier with a circular cross section for uniform flow distribution of exhaust gasses therein whereby the overall volume of the catalyst assembly can be reduced from the conventional catalyst.