Now let's talk about what the specs DON'T tell you.

What is duration? It's a measurement of how long (in crankshaft degrees) the valves are open. But an important aspect is the definition of "open". If the valve is lifted .001 inches (about half the thickness of a piece of paper), it's not really "open" because you don't get any meaningful amount of airflow through such a small opening. So cam manufacturers define "open" when the valve is lifted at either 1mm (about 0.040"), or 0.050". Both are standard, it just depends whether you're using a metric system or not, but they don't always tell you which one they measure to. YOU need to be aware of the issue because that difference of 0.010" can change your specs by a degree or two. You may wish to talk to the manufacturers to get all the information.