Elaine
Same as Blister, but it also depends on your chuck, if you want to mount the jaws in the chuck with it on the lathe. The amount of 'thread' on the chuck determines how much it has to expand to accept the cole jaws, and of course it also affects the amount of expansion that is available for gripping whatever it is you are working on.
As I have said on another thread on my Jet 1642 I cannot mount the large Axi set with the chuck mounted on the lathe, the last jaw to be mounted hits the bed when I am putting it on. In order to clear the bed the jaw needs to be almost fully closed this obviously limits the ability to use it, and setting it up is a pain, so much so that I am considering reducing the size.
I had bought the small axi set but needed something bigger for a large bowl, so bought the large set as well. I use them with a set of accessory jaws in my Precision Axminster chuck and find them great. I turn a bowl with either a spigot or recess, reverse it on the cole jaws and turn of the botom, I think it looks so much better.
Regards
Rod