The plastic caps for laboratory glassware with threads are available in two plastic versions:

Closed plastic caps (screw sealing caps) have seals that are fully coated with PTFE. Plastic caps with hole (screw connecting caps) are combined with matching silicon seals (VQM) with vulcanized PTFE sleeves for passing through tubes with various diameters.

A combination with closed seals (septum) is available for piercing, e.g. for inoculating culture media. All parts can be sterilized.