Plastic Bottle Dumbbell

A tool to which plastic bottles can be attached at the screw holes on both sides. By putting rice, sand or similar inside the bottles, it can be used like a dumbbell. It can also be used like a maraca.

Be careful: if water is put in the bottles, it will leak. The screw threads tend to loosen with repeated attaching and removing, so replace the part periodically rather than using it until it is worn out.