This is a SINGLE 11.11 x 1.78 Nitril O ring for the pump cylinders for a ALTO KEW 4050 XTRA Cold Water Pressure Washer.
It will probably suit other similar Nilfisk-ALTO models of domestic pressure washers.
See the consumer accessory book HERE
Maximise the saving on postage and buy some of the related pressure washer parts below, Or a hose, filters for your Nilfisk or ALTO vacuum cleaner, or a new floor tool and hose.
At the moment standard postage within Australia, is capped at a maximum of $20!