Made from heavy vinyl. A great idea if you travel on a lot of dirt and gravel roads. This neat solution completely covers the gas bottles and tie on by using a cord in the bottom skirt. A good move if you want to make expensive gas contents gauges less tempting to thieves.  They also stop the unused bottle getting grit in the thread. Seen at Lakes Entrance Victoria. The two gadgets not quite in shot are jerry cans! Was this Mrs Bucket's van!