With its thick glass walls and sturdy construction, this 20L bottle/flask is perfect for filtering large volumes of liquid. The thick walls and design enables this flask to withstand vacuum filtration without imploding. Graduated in 2000ml increments on a scale from 4000ml to 16000ml with an accuracy of +/- 5%. Neck size fits a #13 rubber stopper. The hose barb has an O.D. of 1/2”.