Nilfisk Grey-Line IVB5 M and the Nilfisk-ALTO Attix 5 wet and dry commercial vacuum cleaner front castor wheel, it's secured by an Allen screw, which can easily become loose and give the machine an irregular gait, giving the impression the wheel is faulty, when really it only needs the castor fixing screw tightening up.
These are sold singly. And yes you will get a new one, not the one in the photo!!
As it's light, maximise the saving on postage and buy some of the related parts below, such as dustbags and the filters or a new floor tool.
At the moment standard postage within Australia, is capped at a maximum of $20!