unless you buy very good quaility bells, like used in falconry, the type used on cat collars wont be heard, in a perfect world, all will be quite and your hear the bell as the ferret trots off into the hedgerow, but if you have more than one fert down, rabbits hitting nets, holes to re net, dashing over to a longnet, I dont think you'd hear the dangle/tinkle of a bell, a good quaility bell is gonna cost, so why not look into using a loca8tor in conjunction with your mk3, see the pinned popt at top of the ferreting section for pro's and cons