2-PACK PREVENTIC Collar (25") - For Dogs OVER 60 lbs The NEW Preventic 2-pack gives you the convenience of 6 months of protection and you save money as well The PREVENTIC Tick Collar by VIRBAC is the only tick collar that detaches and kills ticks effectively Each collar is effective for 3 months and is a good complement to Advantage or PROGRAM flea control when tick protection is also required. Recommended for use on dogs/puppies 3 months and older.