In Addition, the Sparks Are of Different Intensities.
This is because there is a 1,000 gauss magnet inside each ball. This magnet attracts the charge to it first, then sends it out again as you roll it. This makes for sparks of different intensities from the spikes as you roll them.
Roll one, or both over small or large areas. Tuck one in an out of the way place and zap it; it will transfer the charge off its spikes to your subject!
There are a hundred creative ways to use these.