Crimp seal with PTFE/butyl septum (Pharma-Fix) aluminum seal (with 10 mm center hole), PTFE-faced butyl septum, diam. × thickness 20 mm × 3.0 mm, pkg of 100 ea; find Supelco-SU860011 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-Aldrich