FLSI ballast tubes or sand bags are custom fabricated and filled or shipped empty for freight savings and be filled on-site. Made of Reinforced Polypropylene and other reinforced or non-reinforced materials. Can have typical sand filling, silica only filling, pea gravel filling, or what ever your project may require. With the option for also adding stainless steel grommets for interconnecting ballast tubes together as well. Additionally available are NSF-61 certified materials; such as the liner, sand and hardware, for drinking water applications, along with materials that can resist harsh chemicals and acids. Contact us today to see how FLSI can facilitate your ballast tube needs!