Reducing the diameter of a well bore has many advantages. To achieve this a subsurface well bore is provided comprising one or more expandable sleeve components, preferably expandable liners (27, 271), each expandable sleeve component being fully overlapped by one or more non expandable sleeve component, preferably conventional liners (28, 29), such that the interior of the well bore is cased entirely by non expandable sleeve components (28, 29). In addition the through holes (34a) for downhole lines can be provided within the well head (34) rather than the tubing hanger (33). As the tubing hanger does not need to provide space for through holes and associated mounting couplings, its diameter can be reduced, thus reducing the internal diameter of the well bore by several inches.