That's a woman nylon support hose stocking, calf length. It's like 3 thick as a normal nylon. It filled with pea gravel. Really holds a slope or in this case it's a base fro the Mopane. You can use a regular nylon but I'd suggest you double or triple it up.
cool, thanks for the info. Going try it this weekend when I redo my ADA 60-P