Thanks for all the replies, definitely learned some things. I didn't know you could get different angled ones, kinda cool but I'm not there yet to figure that stuff out. Good to know about using different thickness depending on insert thickness. Makes sense that boring bars don't use an insert seat because of thickness or height but that could also be said that they AREN'T needed or other than to change angle, makes me wonder why most tool holders use them. Hmmm...
So the part the insert seat sets on is called the anvil? Or the insert seat itself is called the anvil?