Hexagon socket wrench, hand-operated. With square drive according to DIN 3120 â C 12.5, ISO 1174. Gedore vanadium steel 31CrV3. VDE insulation up to 1000 V, acc. to EN 60900/IEC 60900, two-ply Check-Tool insulation. 16 â 18 mm insulation overhang. Sizes 27, 30 and 32: diameter d1 is not standardised