great quality, and because they are desinged to be used for Group N and A use, they arent as loud as the cheap and nasty varieties, although they are still loud and give a deep note due to the free-flow nature of them.
in motorsport:
Group N is showroom class (standard vehicles)
Group A is competiton class (modified vehicles)
to qualify for Group N use a vehicle is limited in the modificaitons that are allowed. omp exhausts are allowed because they are designed to be within the noise restrictions.