I' ve never used a " scent lok" type anything, and have had Many. Many deer downwind of me too, with no bad reaction. I' m not saying they cannot work - I tend to think that at least for some period of time the DO WORK to some extent. However, a good hunter will ALWAYS play the wind - suit or Not.

Before you run out and buy one. Set up on a spot (NOT YOUR BEST SPOT) but a spot with a reasonable chance of having a deer come by - BUT set up on the upwind side of where you expect the deer to come from. I think most will find that 50% of the time - downwind deer will have little or no reaction. Also - other times - you will have a clear shot, at a curious deer, that knows " something' s not right" - maybe 25% more . Thge other 1-4 times you get BUSTED - Maybe by wind, smell, movement, who knows.