KYRON ULTRUM LINE-UP 20-40 KG LARGE is a quick and convenient spot-on solution to ensure dogs stay flea and tick free for up to 3 weeks per application. I.G.R. continues to work, killing flea larvae and preventing flea eggs from hatching. For best results allow the product to thoroughly penetrate before washing. Start at the neck between the shoulder blades, part the hair and apply the wholeUltrum Line-Upto the skin. Safe for use on puppies 6 weeks and older.