Compared to Dempsey's arms when he was a prime active champ Harry's are rather puny. (only in comparison mind, but everyone compares Harry to jack.... so be it)
Greb was lean with little visceral fat on his arms. This alone is a good indicator of fast twitch muscle, remember Greb had 118 pro-fights.
Did anyone watch this video and think when is he going to stop this exercise and do something else.....