FARNAM 100505371 128 Count Just One Bite Block Pest Controller Bait Blocks Kill Rats and House Mice Formula Contains The Active Ingredient Bromethalin To Stop Feed Action, Rodents Cease Feeding After Consuming A Toxic Dose Rats and House Mice Usually Consume A Lethal Dose In A Single Feeding, But May Take 2 Or More Days For Them To Die Product Comes In A 4 Lb. Pail