30 Black Rattan Reed Diffuser Sticks Replacement 30 BLACK Reed Diffusers 10 5/8" length, 3mm diameter Cut on ultra sharp blades which allows scent to flow easily 3mm diameter allows maximum wicking of scent Place as many Diffuser Reeds in a jar of reed diffuser oil as you'd like. We find that 3-5 works just fine, but many people add more (8,10,12+). Know that the more reeds you use, the more fragrance is released, and the quicker the liquid is used up.