bougie [bo̅o̅′zhē, bo̅o̅zhē′] Etymology: Fr, candle
a thin cylindric instrument made of rubber, waxed silk, or other flexible material for insertion into canals of the body in order to dilate, examine, or measure them.
Surgeons use anywhere in the measurement called a french of 32-40. Most prefer a 32 unless they double stitch so that the stomach is tighter than that afterwards. A 40 is used for DS because of malabsorption added to the process. It's best to ask the surgeon you pick what size they prefer. You can always ask for a size.
Some surgeons leave a 'pouch' after the sleeve, so some people can hold more than others after surgeries with the same french size.