duct for hood
I have a 20 or 30 year old ge custom 36 venting hood over my stove. I want to replace it but don't know the size of the duct. I can see it? should I wrap a tape measure around it to get the size? I think it Is 6" but not sure I want to buy the same size so ducting won't have to be changed. Can anyone help me determine the size of the duct?