This is a conical reducer nozzle for the Worx WG520 leaf blower. It reduces the outlet diameter from 4" down to 2", concentrating the flow and reducing blower kickback. It slides in from the back of the blower tube, ensuring that it will never come loose during use.

May be compatible with other models so long as the internal diameter at the tube exit is less than 82 mm and the diameter at the inlet (blower side) is > 85 mm.