its content however it may have other shapes such as a cylinder fig1 or a circle of metallic wire the annular body 20 u2032 has a central opening 21 by which an interior of the bag 13 u2032 is accessed the annular body 20 u2032 may be constituted of a pair of parts foldable toward one another to seal the bag shut once the rimmed bag 12 u2032 is filled it is discarded although not shown the annular body 20 u2032 may have tabs on its periphery or connector holes adjacent the periphery so as to be clipped or secured to a waste disposal unit referring to fig3 fig8 and fig1 the central openings 21 of the cassette 12 and of the rimmed bag 12 u2032 are shown having a generally square outline 30 with rounded corners more specifically the generally square outline 30 may be a squircle accordingly the central opening 21 has at least one axial dimension or diameter axis namely passing through the center of the outline shape that is larger than another axial dimension in a transverse plane of the cassette 12 this is shown as a1 being of greater dimension than a2 in fig3 a1 gt a2 in the transverse plane of the cassette 12 the generally square outline of the central opening 21 shown in fig3 i e not perfectly square because of the rounded corners has two diagonals represented by a2 of.