That blade plate will only fit a blade-plate boss that has three attaching screws, with whatever size spigot and whatever pitch circle diameter for the screws, Honda uses on those models. You haven't told us what make and model of mower you have, so we just can't tell. It would be best if you tell us that and attach a picture of your blade-plate boss plus telling us the crankshaft extension (i.e. blade plate spigot) diameter and the pitch circle diameter of the attaching bolt holes.
If it is a commonplace make and model, most likely someone here will be able to tell just from a picture, which blade plate will fit. Usually the lawnmower manufacturer specifies (and maybe installs) the required blade plate boss on the crankshaft extension. Briggs and Stratton will do what the mower manufacturer requires. Victas tend to have a tapped hole in the end of the crankshaft, with no other attaching screws (in my opinion a dismally poor, even stupid, piece of engineering) while Rover and some other manufacturers tended to use three or four screws tapped into the blade plate boss.
