The basic design of the sand bag (aka power bag) has changed over the years, and the outer bag now has handles and removable liners. The inner liners are made from tough polypropylene (which won't rot), with double Velcro fastener at the end of the liner bag to guarantee no leakage. The outer bag is also made from tear resistant polypropylene - important for a product being used outdoors in a wide range of conditions. To keep the bag sealed we've added a heavy YKK zipper. To that we've added a protective panel with snap lock dome fasteners.
3x inner liners, double Velcro fasteners
YKK main bag zipper, with dome fastened protective panel
2x supine grip handles, 3x regular barbell grip handles, 2x end grab tabs (one at each end)