Botox is usually dispensed and placed into muscles of the face based on the number of units. Every vial of Botox Cosmetic starts with either 100 units per vial or 50 units per vial. The product is then diluted out with sterile saline. The amount of saline added to the vial then determines the concentration of Botox in that particular vial. As an example, I always add 2 cc of normal saline to 100 units of Botox for facial injections. This results in 5 units of Botox per every 0.1cc of solution. The size of the syringe then determines how many total units can be drawn into the syringe. So, as an example, if I am going to place 25 units into your entire corrugator complex of muscles in your mid-brow, I would draw up 0.5 cc of product to achieve that dosing. Just remember, never let someone tell you how much volume they are injecting as that tells you nothing about units, unless of course you know what dilution they are using. It is all about units used.