This is the same great biological mosquito larvae killer as QK1 in a slow release pellet. Float this in standing water for extended coverage. Completely degrades - no cleanup. Each dunk treats 100 square foot of surface water, can be broken to treat smaller areas. Unused and stored properly, dunks retain their potency indefinitely. Priced per pack. EPA registered in all 50 states, safe in bird baths, water gardens, or any other standing water. If unused and stored properly, dunks retain their potency indefinitely. 6 pack. Active ingredient Bacillus ringiensis 2.86 Lasts 30 days or more in standing water.