Screw seals ND24 (EPA) are made of PP and are supplied with or without fitted septa made of a variety of materials. They have a 24-400 thread, a 15 mm centre hole or are closed.

These septa 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.

With Ultrabond seals, the caps and septa form an inseparable unit, which means that even a blunt needle is unable to push the septa into the vial.