i don't have much faith in them. i hunt the wind if possiable. had a coon hound that liked skunk killed every one he ran across and brought them back.and stunk like he.. will 3 minutes later he could have a coon treed. thats a good nose and deer have it to.air currants do funny things but if a deer smells you he's most likey gone.i have had deer downwind and came in but i bet they didn't get my scent.