Guardian One is a monthly flea prevention solution for dogs weighing 25-46lbs. It contains 13 capsules and utilizes Nitenpyram and Lufenuron, both trusted and effective ingredients. Nitenpyram begins working in just 30 minutes while Lufenuron protects for 30 days. These capsules do not contain any preservatives or artificial flavors and are made with all-natural, high-quality cuts of meat. The unique airtight bottle cap and gelcaps design reduces air penetration, ensuring long-lasting effectiveness. Guardian products are scientifically formulated and backed by years of expertise in the pet supply industry.