The UIC | O-ring w/ PTFE Outer Centering Ring (KF50) is a KF50 vacuum flange seal assembly specifically designed for UIC KDL5 molecular distillation systems, combining an inner elastomeric O-ring with a PTFE outer centering ring for chemical resistance across the full flange face. PTFE construction resists degradation from the solvents and heat transfer fluids used in UIC molecular distillation. An OEM UIC replacement sealing component for KF50 vacuum connections on KDL5 distillation systems.