Off Properties behavior

Working on a somewhat complex model. When I add a cylinder and enter a size, say 25.4mm radius, the result is 1/2 what it should be, asa 25.4mm diameter... When I add a cylinder to a new document and copy paste it over to my model, it comes in with the proper 25.4mm radius. I have not scaled my model in the fields at the top of the properties window. What gives?
I generally add things outside hierarchy objects created and size and drop them into hierarchy as I need to organize. I never noticed before but O saw that, when I use the scale tool, the values at the op of the Properties tool window change. For this model, I've sized the most needed objects in another document before bringing them into my model to boolean. This seems to work.