IronMind - Small Tough-As-Nails Cordura Sandbag 18 x 30
Rock on, indoors or outside, they're made for tough stuff, like lifting, carrying, and loading--and unlike a stone, they allow urban dwellers to do cavemen-centric training anywhere. Plus, they train your grip each time you work out.
The Small Sandbag is 18" x 30", designed to conveniently hold 100 lb. of sand or less if you'd prefer, in a shape that's well-suited for a weight in this range.