The professional size is 25 ml compared to the 16.3 ml of the XL size bottle and 10 ml for the regular size bottle. I paid $23 for the XL size bottle. The professional size retails for $29 at urbandecay.com and Sephora. Since I am a huge fan (click here for my product rave review), I promptly placed my order from Sephora. Here are some comparison pictures.