Don't be alarmed that your bottle of essential oil is not filled to the top! Air is necessary for the reducer cap and pipette to work successfully. The bottle volumes are as follows: Vials used for 1 mL offerings hold 0.0625 oz.(1/16 dram), 5 ml bottles hold 10.25 ml; 10 ml bottles hold 17 ml; 15 ml bottles hold 24.5 ml. Each bottle is hand filled with at least the amount of essential oil the label indicates. We have been known to be generous with our portions. Our bottles are not filled by weight.