We recommend you change these frequently as the uneven surface will compromise the back seal.
We would also recommend that when you change the PTFE strip, you change the drive belts at the same time. At Kenray,
we’ve developed many variants of the TNA back seal to ensure, proper sealing, particularly with Matt and paper film.
In the example, shown the PTFE is replaced by stainless steel, which also assists in keeping the tube stable.
The insert in the center can be replaced with different materials to seal different films.