Mk 3 is the dogs danglies,I use it all the time be it terriers or ferrets and can home in to 6 inches all the time.They're a great bit of kit.I am amazed when some say they cant use them,they're simple to use,and way better than the mk1.I got rid of my mk1 for the mk3 and have absolutely no regrets.But I was brought up the old ways,ferret bells and patience,so if the worst comes to the worst It doesnt phase me if the locator packs up,saying that, I wouldnt leave home without it.