Valves I purchased around 2002 or 2003 didn't have this feature but since then, the valve stem is narrowed to about 1" up from the bottom of the valve to increase air flow over stock valves. Highly recommended for anyone into upping the performance of their iron head engines... While I learned this was a performance benefit over the past year or so, I didn't know the SI valves came this way already since I have had them direct-shipped to my machinist the last few times I've rebuilt motors.
Sorry for the fuzzy video, my phone's video recording isn't that great but I think you can see the difference.
