Yes. You hand them out to your fellow antifa. They light the fuse while they're holding it in anticipation of throwing it. But the fuse burns in half a second. Whoops!
With a smaller shell casing you could also put this inside it to function as a pressure vessel (even 1mm will give you vastly more boom). Still need to layer it with your pretty jewelry cubes though. You can't layer the inside so they'd have to go outside but then you need a way to disguise it as a normal shell.
Also, your suggested fuse says the duration is .5 seconds per foot. WTF?!
https://www.amazon.com/inch-HOLLOW-STEEL-threaded-weldable/dp/B07VCMF47L
With a smaller shell casing you could also put this inside it to function as a pressure vessel (even 1mm will give you vastly more boom). Still need to layer it with your pretty jewelry cubes though. You can't layer the inside so they'd have to go outside but then you need a way to disguise it as a normal shell.