2KG can be tied to the wrist to practice boxing and can also be used for initial running training. Normal trouser legs under 3KG (including 3KG) can be covered, which is not easy to find. 4~5KG needs to wear heavy sweatpants to cover it.
It's the kind of sand leggings sold in stationery stores or shopping malls. If the steel plate is too hard, it is easy to grind meat.