"extractor fan busted so purchased a new one never checked the flue size,when it arrived the flue kit was 120 mm hole in wall to big,screwfix to the rescue 150mm to 120 mm reducer £1.34 fitted upside down JOB DONE"
"This was used as part of two pieces to reduce an extractor from 150 to 100, so I could attach an extractor to an external vent. The kit provided with the (non-screwfix) fan only reduced to 125 !! It was german !!"