Altmann Analytik ND20 crimp cap aluminum, magnet. gold, 5mm hole, with butyl, dark grey, 55° shore A, 3.0mm, 10x100pc/PAK

Special, moulded Butyl/PTFE liner that is only laminated with PTFE in the contact area towards the sample. On the glass rims the elastic Butyl achieves a very tight seal.