They tend to have the same distance between screw holes if that is what you mean by standard fitting. However there are different shapes of loo - rounded nose and pointed nose for example. If you get the wrong shape it won't fit properly, and it won't look right even if it does fit. Also there are different sizes of toilet - our two are different sizes and one seat wouldn't fit the other. I would measure the length, width at the widest point, and distance between screw holes just to make sure.