Chang Lightspeed filters : what are the "tubes" inside?

Does anyone know what the "tubes" inside the Chang Lightspeed filters are?

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I've been looking for more information to no avail.

Chang just indicates AC will flow through the tubes once, twice, thrice, etc... according to the level of filtration (Level 1, Level 2, Level 3, ...) but I'd like to know more about these tubes.

Do they put anything *in series* to the AC or are they filled with filtering materials wrapping the AC cable?

Thank you!