This has been around for a while in certain circles, but it is effective and very easy to do, skip the whole grenade thing, you could actually go to jail just making and carrying it. Just use the cardboard cylinder, a toilet paper roll will work but not as well as the heaver cardboard roll. I am not sure why more demonstrators have not used this more, it is effective, and would cause real problems if used inside a building or bus, or on the subway. Just one more thing we will have to keep an eye out for.
from CTI Consulting https://www.youtube.com/watch?v=fdeXcGkqT_4