Hartz UltraGuard ProMax Flea and Tick Collar for Dogs and Puppies 12 weeks of age and older kills flea and ticks, repels mosquitoes, and prevents flea eggs from hatching. The unique, patented flea and tick collar design achieves maximum comfort with its soft and flexible texture. The ProMax flea and tick collar features a Dual Buckle System that ensures the collar remains securely fastened. The flea and tick collar is also water-resistant so your dog can still enjoy baths, playing in the rain, or swim time. Each tin contains two 6 month flea and tick collars to provide consecutive protection for up to 12 months.