A surface treating head comprising a first body defining an inner aperture, and a support body defining an outer aperture, the outer aperture surrounding the inner aperture, and the support body being moveable relative to the first body to allow for relative movement between the inner and outer apertures in a substantially vertical direction, wherein the surface treating head further comprises a bellow seal provided between the first body and the support body that maintains a substantially airtight seal between the first body and support body irrespective of their relative positions and movements.