I hear anything less than the 6000 isnt as good 'strength wise ' as a elgin 21-4n pro stock valve. I think the Frerrea 5000 has a better finish than a budget pro stock, but I have also spun them in a press and polished them ...seeing a small gain afterward on the flowbench, just surface finish. Which is pretty much worthless outside of a dyno test magazine rag because as soon as you put miles on it...its not smooth anymore.