The pluggable electrical apparatus, formed in particular as a surge arrester (A), has an axially symmetrical housing (1) with a housing axis (7) running in the plugging direction, a flange (5) for fastening the apparatus housing (1) on a housing (30) of a high-voltage installation (H) and an axially symmetrical active part (6). In order to make it possible for this apparatus (A) to be fitted into the high-voltage installation (H) in a simple manner, the flange (5) is formed into the apparatus housing (1) and the active part (6) is mounted displaceably in the axial direction in the apparatus housing (1) and held with a prestressing force with respect to the apparatus housing (1) before a plug-in connection is formed.