Crimp neck and headspace vials ND20 with rounded or flat bottom made of clear and amber first hydrolytic class glass need to be able to withstand very high internal pressures and, as a result, their walls are generally 1.2 mm thick. The vials are available with a flat DIN crimp neck or with a bevelled neck (HS neck).

On the flat DIN crimp neck, liners have a greater contact surface, which ensures a better seal. A bevelled HS neck is required if the overpressure safety seal system patented by Perkin Elmer is used, since excess pressure can only be reliably dissipated in vials with an HS neck.