32mm backpack vacuum cleaners hose plastic click ring for hose bent tubes or hose cuffs.
They secure the white threaded Hull in place, with two dimples. Simply depress in the dimples with a screwdriver. They are also on cheaper barrel vacuum cleaners, such as the original VAX.
In the second picture, it's at the bottom of the photo.
As it's light, maximise the saving on postage and buy some of the related parts below, such as the paper dustbags and the filters or the whole clean air pack with bags and set of filters in it.
At the moment, standard postage within Australia is capped at a maximum of $20!