Cool Things Update! - Sandbells

So I ran into a new piece of workout equipment that is an alternative to dumbbells! I usually like to keep an eye out for alternative fitness tools useful for when I'm traveling or don't have access to my personal equipment or a gym.

Anyways, what I found are called "Sandbells" (View), and consist of neoprene bags filled with specific amounts of sand - ranging from 5-50lbs. Apparently, one can order them either pre-filled or empty (to save on shipping costs) and can use them as dumbbells, medicine balls, or kettlebells. They seem pretty handy as an alternative, but I don't know how convenient they would be for travel..