These 4L PYREX® pear-shaped glass separatory funnels have Polytetrafluorethylene (PTFE) No. 8 Product Standard stopcocks and strong, hollow No. 38 Standard Taper glass stoppers. The PTFE plug fits into the micro-finish barrel. The plug also reduces freezing problems and grease contamination. For replacement glass Standard Taper stoppers, see No. 7650; for PTFE stopcock assemblies, see No. 7681.