Gaugemaster GM201 Ballasted Underlay - N Scale Grey (Flexible 5m Roll)
5 Meters (16ft aprox) of foam underlay with granite ballast bonded to the foam. Very flexible and easy to work with thanks to sleeper indentations. The track just falls into place and gets pinned down using longer pins like the GM67. For additional effect you can use the corresopnding loose ballast to fill in any areas which require more ballast such as yards or stations.