With Series 1C the tube ID is pushed onto the internal sleeve as in 1A, but the clamping mechanism is different. A PTFE sealing ferrule creates a tight fit while behind it is a PEEK cutting ring. As the nut is turned, contact pressure between tube and cutting ring increases, effecting a friction locked connection ideal in high temperature environments or where vibration maybe a concern. Series 1C is used with more rigid tubes e.g PVDF, PFA.