I just bought pair of new tyres (still in the post).. And I just saw something called specialist fitment on blackcircles. Whats the difference between a 'usual' tyre and one approved for Merc? I have stock Merc rims bought with the car from MB dealer but replaced stock Contis with Goodyear 10yrs ago and never felt better on the road although I doubt those were Merc fitment .. So whats the point? Or is it just marketing blur?