What are those circle black tags some hunters where on their hats in hunting shows?

Were watching hunting videos and all of the guys have these vented black circle tags clipped to the back of thier hats. What are these?What are those circle black tags some hunters where on their hats in hunting shows?
they are scent wafers they pin to your hat or clothing and they smell like dirt and they come in alot of different scents too. i use themWhat are those circle black tags some hunters where on their hats in hunting shows?
They are scent wafers. They are used for several different purposes. Some have scent in them to attract deer, elk, bear, or to make you smell like the woods!.