Nilfisk-Alto Attix 360 and Nilfisk IVB 3M vacuum cleaner filter holder. This part holds the filter in position and has the float shut off inside for the Nilfisk-Alto Attix 3 and the Nilfisk-Alto Attix 550, 750 etc as well as the Nilfisk IVB3 M.
It spins on by hand, no spanner needed.
There are also other models and brands that it will fit, including WAP and Festo Hilti Makita and Stihl branded vacuum cleaners
It used to be part number 302000472 However, for a cheaper alternative use Pn. 302000662
As it's light, maximise the saving on postage and buy some of the related parts below, such as dustbags and other filters or a new floor tool or other accessories.
At the moment, standard postage is capped at a maximum of $20 within Australia.