Autosampler Vial Caps and Closures. Fisherbrand™ 11mm PE Snap Ring Seal, Transparent, Center hole, Assembled septum. Polyethylene caps are chemically inert and suitable for most chromatography applications. Pricing and Availability. Fisherbrand™ 24mm PP Screw Seal, White, Closed Top, 24-400 Thread, Assembled Septum. Ready to use combination