David Grays Rat & Mouse Killer Pellets David Grays Rat & Mouse Killer Pellets is an effective and highly attractive pellet rodenticide. Using the active ingredient Warfarin, this bait will be irresistible to any rodents infesting your property. How to Use Place small heaps of the pellets where rats and mice are commonly spotted. Where possible, place them in cupboards and along walls. Ensure that other foodstuff is covered from rodents when baiting, to ensure that the pellets are the more easily accessible option for the rodents to eat. Always use caution when applying bait, place in locations that are inaccessible to children, other animals, and birds. Do Not allow chemical containers or pellets to get into drains, sewers, streams, or ponds. Wash hands after use, and always follow directions on the label.