Just One Bite II kills mice, roof rats and Norway rats. Norway rats and house mice may consume a lethal does in one feeding. The active ingredient is bromadilone, a second-generation anti-coagulant rodenticide that causes internal bleeding. Also treated with methioprene to protect the bait from infestation by insects. Contains rodent"s favorite foods - grains and seeds. Death is delayed 4-5 days so there"s no bait shyness.