mike_s:or to widden that question a little, if the parts are not "exact" cosmeticly the same, are they functionally a copy of the same? (if that makes sense)
I haven't actually tried to"exchange" parts, some "eyeball" close but I wouldn't recommend that as a definative answer. I wouldn't recommend using other than Apeks parts in a Apeks reg and the same goes for any brand.