4 T beads to 1 T FO (I actually go by weight, but that's what I started at to get weights. Personally, I love it when I open the door and the scent knocks me in the face, but I have had people leave them in the bag, open, under the front seat or hang it from the clothes hook in the back of an SUV. If the windows are tinted it won't get full sun, just enough warmth to release the fragrance.