N 20 Aluminium crimp cap, silver, center hole Butyl dark gray/centrical PTFE-lamination gray high purity Hardness: 50° shore A Thickness: 3 mm pack of 100

Similar product as 70234, however, with a higher analytical purity. These closures with molded Butyl/PTFE septa are only laminated with PTFE in the contact area with the sample. Thus the elastomeric Butyl can achieve on the vial's glass rims a very tight seal, while in comparison a completely PTFE covered septum would have a very slippery surface on the glass and could easily be twisted around.