Crimp seals ND13 are made of aluminium. They are clear lacquered and have a 6 mm centre hole, a centre tear-off or complete tear-off. They are supplied with fitted septa made of a variety of materials.

The septa made of silicone white/PTFE red are temperature-resistant from -60 °C to 200 °C and have better purity than septa made of natural rubber, butyl or red rubber. However, they have less effective resealability properties and are therefore more suitable for single-injection applications.

The septa made of butyl red/PTFE grey are temperature-resistant from -40 °C to 120 °C and have excellent chemical properties with regard to cleanliness.

On Pharma-Fix seals, it is only the butyl areas that can come into contact with the sample, are PTFE coated. The areas that abut the edges of the glass are not coated. This ensures a particularly good seal.