ProMeris Duo 100.5 mg + 100.5 mg Spot-on for small dogs ProMeris Duo 199.5 mg + 199.5 mg Spot-on for medium sized dogs ProMeris Duo 499.5 mg + 499.5 mg Spot-on for medium/ large sized dogs ProMeris Duo 799.5 mg + 799.5 mg Spot-on for large dogs ProMeris Duo 999 mg + 999mg Spot-on for extra large dogs