I picked up a bunch of collets today and there are two that I'm not sure what kind they are. They are 3.5" long and .8125 wide (approximate as I don't have my calipers with me). One is a Porst Bros of Chicago and the other is a Rivett and says 4 NS on it. Is the 4 NS the kind of collet? I haven't heard of this one and didn't see anything when I searched. Can anyone help me identify what type of collet as well as an idea of which machines have the same?