Red rubber/Polytetrafluoroethylene (PTFE): improved level of cleanliness compared to natural rubber. PTFE coating ensures compatibility.
Natural rubber/Ethylene Tetrafluoroethylene (TEF): features excellent resealing properties.
Silicone/PTFE: cleanest solution for contaminant free sample handling; autoclavable, too.
PTFE/Silicone/PTFE: PTFE laminated to both sides of high-purity silicone to prevent coring.

Please Note: Vials, caps, and septa formerly under the Kinesis brand have now been rebranded Cole-Parmer. All the same great features and specifications, just with a new and improved look.