Mar 29, 2022 · 18mm Screw Thread top septa is used PTFE and high-quality silicone rubber or ultra-pure silica as raw materials, the gasket is guaranteed to be non-toxic. 1. A rounded bottom is more sturdy and thus more resistant to the high pressure within the vial during the heating process. 2. 10ml, 20ml clear or Amber precision thread vial. Get Price 22-03-29