silver aluminum seal, open center (10 mm opening), diam. × thickness 20 mm × 3.25 mm, tan PTFE/silicone, pkg of 100 ea. Supelco. pricing. SDS. 27229. silver aluminum seal, open center, diam. × total thickness × PTFE thickness 20 mm × 3.2 mm × 2 mil, white PTFE/silicone, pkg of 100 ea.