A flexible cylindrical shape made from expanded polyethylene foam. Intended to provide expansion joints or fillers in concrete. Very versatile for use in scenic applications. Available in diameters from 1/4" to 2". Sliced cross-wise can represent rivets, buttons, or bolt heads; sliced longitudinally can simulate 1/2 or 1/4 round molding.
Limited sizes likely available at Home Improvement Centers.