This is a genuine "pre motor" washable filter that fits a DC20 cylinder vacuum cleaner. It measures 152mm in diameter. 

Part number 917819-01  17819-01  91781901

Replaces older style 2 parts filter with this one part, seals better too.

Also known as a pre motor filter or washable filter. Located at the top of the machine. This is the new style of filter being supplied by Dyson. The older style filter has been discontinued.

Fits Dyson Models DC20

Serial numbers starting with 360 369 371

Supplying parts to New Zealand NZ