A valve assembly comprising a housing and a valve member mounted within the housing rotatable about an axis and between at least a dispensing position and a further position, for instance a volume selection position during which a material can be withdrawn from a container, and, preferably, a seat for mounting and guiding the valve member within the housing, wherein at least one of said housing, valve member, and seat is made of a synthetic material and the assembly further comprises a spring, which urges at least two of said housing, valve member, and seat together.