This Eberspacher ducting valve cable requires ideally a 12-13mm diameter hole drilling for mounting onto a flat surface. It is able to be mounted through a surface depth of 12mm.
It should be noted also that a smaller 5-6mm hole is drilled to locate the spigot locator on the reverse of the fascia plate. This prevents the mechanism as a whole from rotating when the control knob is turned clockwise or anti-clockwise.
I have included some additional images on the product description link below to help explain further
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