PYREX No. 19 PTFE Standard Taper Keyhole Stoppers,
Corning 'These chemically resistant No. 19 PYREX® keyhole stoppers are made from polytetrafluoroethylene (PTFE) and conform to Standard Taper stopper dimensions. The color-coded keys make sorting and selecting the correct size much faster and easier. These stoppers may be used in place of conventional glass Standard Taper flask stoppers. - COG
