This product uses the active ingredient bromethalin, an acute active capable of controlling anticoagulant resistant house mice. It can be used indoors or outdoors. It meets the EPA's highest level of security and quality. This refillable bait station comes with 16 Bait Refills in 1 oz blocks. It comes with a clear lid for easy bait monitoring. When the bait is gone, simply refill. Each Block can kill up to 12 mice. Proven to be tamper-resistant to kids and dogs. Compliant with the EPA's Risk Mitigation Decision for Rodenticides.