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.
Click and Clean is a method Nilfisk-ALTO and KEW and WAP and Gerni use to connect accessories. There are different Generations and they won't connect together over cross generations.
See the consumer accessory book HERE
Maximise the saving on postage and buy several Puregiene toilet rolls a box of Tissues and some soap or maybe some packets of dustbags, or a hose or a new floor tool, or some other accessories!
At the moment standard postage within Australia, is capped at a maximum of $20!