A capsule for holding a substance which is required to be held in hermetic isolation, the capsule including:a first capsule portion of flexible material for holding the substance, the first capsule portion having a closed end, an opposed open end and a predetermined length dimension defined between the ends thereof;a second capsule portion of flexible material having a closed end, an opposed open end and a predetermined length dimension defined between the ends thereof, which is shorter than the length dimension of the first capsule portion;a cap which is secured to one of the first capsule portion and the second capsule portion so as to define an additional chamber within which an additional substance is held;the closed end of the second capsule portion being located within the open end of the first capsule portion such that a region of the second capsule portion overlaps a region of the first capsule portion so as to close off the open end of the first capsule portion and define a chamber within which a substance is held, wherein the open ends of the first capsule portion and the second capsule portion are aligned flush with one another.