Just to point out John that Supernova chuck has not been in production or sold for about 15 or 16 years (or more). The Supernova II which took its place uses a key just like the Vicmarc. Don't forget that the Vicmarc originally was a copy of the nova chuck. The Vicmarc cost twice what the Nova costs and in my own opinion is no better than the Nova. I have Nova chucks, Vicmarc chucks, Oneway chucks, Axminster chucks and Bulldog chucks. Notice the s' multiples of each and I do not consider one better than the other I choose which to use by the jaws that are on it.