Hexagon key 2.5mm ISO2936 hardened nickel-plated Hexagon Compatibility: Hexagon key 1.5 for M2 hexagon screws Hexagon key 2.0 for M3 hexagon flat screws Hexagon key 2.5 for M3 screws and M4 hexagon flat screws Hexagon key 3 for M4 hexagon screws Hexagon key 4 for M5 hexagon screws Hexagon key 5 for G1/8 screw plugs and P&C 1/8? connections Hexagon key 6 for G1/4 plug screws and P&C ¼? connections Hexagon key 8 for G3/8 screw plugs