 Slappers, instead of directly using the exploding foil to detonate the initiator explosive, use the electrical vaporization of the foil to drive a small circle of insulating material such as PET film or kapton down a circular hole in an additional disc of insulating material.At the far end of that hole is a pellet of conventional initiator explosive.The conversion efficiency of energy from electricity into kinetic energy of the flying disk or slapper can be 20–40%.