We, of course, provide column capitals and bases as separated products, but we cannot guaranteed fitting on other shafts, including your own, there are several reasons, and one of them is the diameter, usually all these products comes 3/8 in. smaller than factory measurements, and secondly, all our hand painted columns are tapered, it means that the shaft top diameter is smaller than center or bottom, beside there’s an assembly point on shaft top with no exact diameter at all.