The present invention relates to an insert (23,40) adapted to fit on a breast-receiving funnel of a breast pump. The insert (23) comprises a circumferentially extending resiliently deformable wall (26) which defines a teat receiving space (33) and against which a users teat is locatable, the insert being configured to define a pressure chamber (38) between the resiliently deformable wall and a breast receiving funnel (12) when the insert is fitted on a breast receiving funnel, wherein said wall is configured to deform towards a users teat located in the teat receiving space in a predetermined manner when a pressure difference is applied between the teat receiving space and the pressure chamber such that a peristaltic action is applied to a users teat, to aid the expression of milk therefrom.
