SandBells are a cross between dumbbells, kettle bells, and medicine balls and they're amazingly versatile. You can lift them in an almost unlimited number of ways, toss them in the air, and do all sorts of different tricks. If it falls on your foot, it's ok because it's just sand in a stretchy neoprene casing. The shifting sand works the stabilizer muscles in your core and results in more calories burned compared to the same workout with conventional weights. The Sandbell is also easier to store than a dumbbell; you can stack it up or put it out of sight.