I've used these collars on my 2 German Shepherds for the past 2 seasons and no fleas or ticks. The odd tick that I have found in their fur is dead when I find it. They last for an entire warm weather season (8 months) and as a result, are very economical. I can't say enough good stuff about these collars, and although it may sound like it, I don't work for the company that makes them. Can't go wrong with these collars as far as I'm concerned.