An insulation spacer for a gas insulated device includes an insulator disc and an armature extending around an outer periphery of the insulator disc and holding the same. The armature is ring-shaped defining a ring axis and includes two ring base surfaces extending substantially perpendicularly to the ring axis; and a ring inner surface being arranged between the two ring base surfaces and facing the ring axis. Further, the ring inner surface includes at least one protrusion directed radially inwardly towards the ring axis, the at least one protrusion being shaped such that it locks the insulator disc in the armature against movement in both directions parallel to the ring axis.