These Corning PYREX® cylindrical separatory funnels are graduated to show approximate capacity, have a micro-finish No. 4 Product Standard PTFE stopcock and a strong, lightweight Standard Taper glass stopper. The PTFE plug fits into the micro-finish barrel. The plug also reduces freezing problems and grease contamination. Pyrex cylindrical glass separatory funnels are available in 100mL 125mL, 250mL, 500mL and 1000mL sizes.