Nilfisk industrial vacuum cleaner spark arrestor for quenching sparks before the vacuum cleaner filter. The body is plastic with a metal plate in the centre which works as a baffle.
Hole is 50mm Inside Diameter, and 58mm outside diameter.
I've previously had occasion to use spark arrestors on linishing machines in machine shops, where the polishing of chrome hydraulic rams with belts of emery paper generates a trail of sparks that have passed into the vacuum cleaner and set it on fire.
At the moment standard postage within Australia, is capped at a maximum of $25, so maximise the saving on postage and buy something in related items below!