A kit of parts to assemble a dispenser of material, comprising: a tubular body of substantially invariant internal cross-sectional shape; a bung which: is adapted to slide within the tubular body; and has a periphery which is adapted to form a first sliding seal between that periphery and the internal side walls of the tubular body; and a base cap having an aperture through it, the base cap being adapted: for mounting at a first end of the tubular body so as to substantially occlude that end; and to allow airflow through the aperture into the tubular body as the bung moves in a direction away from the first end of the tubular body; and the base cap having a valve carrier in place over the first end of the tubular body, the valve carrier comprises a first valve which permits airflow only in the direction from the exterior of the tubular body to the interior of the tubular body in use, characterised in that the first valve comprises a portion which is substantially more than half of a hollow sphere, the periphery of which is contiguous with a cylindrical portion of the first valve, and in that the periphery which is adapted to form the sliding seal comprises at least one of: a radially-extending circumferential seal; a radially-extending scraping and sealing blade; and a radially-extending locating and alignment ring, which is located between the radially-extending circumferential seal and the radially-extending scraping and sealing blade. a tubular body of substantially invariant internal cross-sectional shape; a bung which: is adapted to slide within the tubular body; and has a periphery which is adapted to form a first sliding seal between that periphery and the internal side walls of the tubular body; and is adapted to slide within the tubular body; and has a periphery which is adapted to form a first sliding seal between that periphery and the internal side walls of the tubular body; and a base cap having an aperture through it, the base cap being adapted: for mounting at a first end of the tubular body so as to substantially occlude that end; and to allow airflow through the aperture into the tubular body as the bung moves in a direction away from the first end of the tubular body; and for mounting at a first end of the tubular body so as to substantially occlude that end; and to allow airflow through the aperture into the tubular body as the bung moves in a direction away from the first end of the tubular body; and the base cap having a valve carrier in place over the first end of the tubular body, the valve carrier comprises a first valve which permits airflow only in the direction from the exterior of the tubular body to the interior of the tubular body in use, characterised in that the first valve comprises a portion which is substantially more than half of a hollow sphere, the periphery of which is contiguous with a cylindrical portion of the first valve, and in that the periphery which is adapted to form the sliding seal comprises at least one of: a radially-extending circumferential seal; a radially-extending scraping and sealing blade; and a radially-extending locating and alignment ring, which is located between the radially-extending circumferential seal and the radially-extending scraping and sealing blade. a radially-extending circumferential seal; a radially-extending scraping and sealing blade; and a radially-extending locating and alignment ring, which is located between the radially-extending circumferential seal and the radially-extending scraping and sealing blade.