This 2-pin (round) unit plugs into the mains and, with a tablet inserted in the slot, slowly emits an insecticide which is both harmless and odourless to humans, but is extremely effective against biting insects. Ideal for use during the night (each tablet will last for about 8 hours before needing to be replaced). The Plug-In Killer should be used indoors for maximum effect. Repellency Time: 1 tablet provides up to 8 hours protection.Repels: Mosquitoes, midges, bed bugs and other biting insects.Comes with 15 tablets.