I would assume that stummers are about the diameter of an oversized grenade (given this universe's propensity of oversized common parts). Think starwars thermal detonator size, just a 'little too big' to fit in your hand properly. absolutely criminal of the designer to make a fumbly explosive :P<br/><br/>These things, like screamers gotta be small enough to hide and have practical application, screamers are 'trap like'. stummers are the reverse of screamers, and need to be portable to be useful, since your trying to be sneaky. even if you have to drop it for it to be practical, you dont want to chuck a 20lb backpack of metal open. If guards are near enough to hear it, odds are they can see it too.