IIRC The K&N part number for our oil filter is 401.
Its the same filter as the old Z1 and Z650 used, as well as many Honda's (Early Gold Wing CB750 etc)
As Gump said the filter sits into a housing in the sump pan. the 'cup' being a sort of baffle that persuades the oil to flow through the upper sections of the filter.
The new one should come with 2 O-rings, one for the bolt and one for the cover plate, but often (as they are 'the same' as the Honda filters) the O-rings are sightly too large (in circumference)