This is for vacuuming large heaps of material, such as mineral sands, grain, gravel. etc. It allows air to pass with the product, as otherwise the hose can become blocked, especially when using long lengths.
Probably most suited to the NilfiskCFM127 and the NilfiskCFM137 and the NilfiskCFM S2 and the NilfiskCFM S3 industrial vacuum cleaners using 40mm hosing, as well as the NilfiskCFM 118 industrial vacuum cleaner
At the moment standard postage within Australia, is capped at a maximum of $20! So, maximise the saving on postage and buy some of the related parts below, such as other accessories, or some dustbags and filters.