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The small black controller unit with a dial controls the temperature, this is adjusted depending on the thickness what plastic you are using. The video shows the heat mat under the film and you can see the lines and curved seal mark of the roller after the heat was applied. If you were to seal a plastic bag or tubing in a straight line you would be better to use and Impulse sealer or Constant heat sealer.
![](https://i.ytimg.com/vi/nxWtSoZCIxU/maxresdefault.jpg)