Bedfordshire Police are the latest force to start using the Taser electrical stun gun.
Two probes trailing a copper wire deliver a shock to incapacitate
From Thursday the gun will be issued to specially-trained firearms officers to deal with violent and armed offenders.
Tasers discharge two barbed probes which, on contact with clothes or skin, deliver a five-second shock designed to disable rather than injure.
On Tuesday the Cambridgeshire force announced it was to start using the stun guns for the first time this week.
Police say Tasers are particularly effective against violent offenders as it disrupts muscle control.
Critics have raised safety concerns about the guns which can send 50,000 volts of electricity through the body.
The electricity causes temporary incapacity but some critics believe they can be lethal.
The makers and the police insist the weapons only give a low level electric shock, which does not have any long-term health implications.