PreStrike Mosquito Torpedo 5 pack prevents mosquito development up to 2 months. It is effective in killing developing mosquitoes in standing water before they become breeding adults. Each treatment releases insect growth regulator into the water and won't harm animals, fish, humans or vegetations. It can be used on animal troughs and it has a no float design and no unsightly debris. To use, add 1 tablet per 100 sq. ft. in standing water, for larger sites, use 2 applications. This product comes with 5 in a pack.