Zehnder ComfoTube ComfoTool Cutter for Dia 75 90mm VPP10077 adding to the already simple adding to the already simple installation procedure and the iris shutter design makes switching on and off almost silent and helps reduce external noise ingress Timers these carry on running for an adjustable period usually about twenty minutes after it has been switched off but this can be set to anywhere between two and thirty minutes Zehnder P N 990 000 110 Zehnder ComfoTool cutter comes complete with interchangeable attachments to enable a professional and clean cut every time for both the Zehnder ComfoTube ø 75 mm or Zehnder ComfoTube ø 90 mm ductwork