Its steel, and Ducati offer a magnetic tank bag. 16 litres capacity, the warning light comes on when two bars are showing. Which is just over one imperial gallon or 4 litres.
I think perhaps the dreaded ethanol may have had something to do with some of the failures. Particularly on old bikes.Nah, Ducati liked replacing so many plastic gas tanks that they decided to keep on doing it. It is their way of keeping in touch with their customers. >