Disclosed is a centrifugal separation chamber (100) rotatable about an axis (AR) and having a variable volume separation space (116) therewithin and a port (102) in fluid communication with the volume for filling and emptying the volume, the chamber including a relatively rigid portion (104) proximal to the port which has walls defining a part of the volume and arranged to provide reducing dimensions of the volume toward the port, the chamber further including a flexible portion (106) distal to the port for providing said variable volume, the flexible portion including a mechanical interface (110) for transmitting movement to the flexible portion to cause said variable volume.