A surge arrestor includes an active part extending along a longitudinal direction of the surge arrester, a first electrode having a first interlocking part, a second electrode resting against a second end of the active part, a flexible insulating housing, and a second interlocking part formed on an inner surface of the flexible insulating housing. The flexible insulating housing includes: a support member mechanically connecting and supporting the assembly of the first electrode, the active part and the second electrode, which has a plurality of supporting elements being arranged parallel to the longitudinal direction of the surge arrester and being arranged laterally at sides of the assembly of the first electrode, the active part and the second electrode, and an insulating expandable part with a plurality of sheds extending outwards, being moulded around the support member and being spaced apart from the assembly.