in more detail below in the coaster 100 embodiment shown in fig1 6b the coaster 100 may include stiffener features 140 150 spaced apart at regular intervals along the outer fluid barrier interior surface 122 and the valve flange exterior surface 134 these stiffener features 140 150 may be configured to support the outer fluid barrier 120 and the valve flange 130 when the coaster 100 is coupled to a container however it will be understood that in other embodiments the coaster 100 may include some or none of the stiffener features 140 150 for example the coaster 100 embodiment shown in fig8 a and 8b includes stiffener features 150 but not stiffener features 140 as one non limiting example the stiffener features 140 150 may act to support the outer fluid barrier 120 in an upright orientation as when a container is pressed downward and inward or otherwise installed the stiffener features 150 may extend inward to press against the container and provide a gripping force to help act as mounting features further the presence of the stiffener features 140 150 may support a cavity that may otherwise collapse upon installation of a container otherwise an outer surface of the container may press outward expanding the valve flange 130 against the outer fluid barrier 120 collapsing the cavity this cavity may serve as a reservoir and thus may advantageously be preserved for fluid entrapment and storage however it will be understood that the stiffener features 140 150 are optional adequate stiffness of other coaster components may enable the coaster 100 to preserve the cavity without the stiffener features 140 150 in a.