Size: 2.5 MMLong Arm Length Range: 53mm - 56mmShort Arm Length Range: 17mm - 18mmMaterial: Hardened Alloy SteelA Hex Key Is A Six-Sided Shaped Bar Bent At A 90 Degree Angle At One EndDesigned To Be Inserted Into A Like-Sized, Hollow Recess Of A Socket Screw To Manually Tighten Or Loosen The FastenerEither Side On The Key Can Be Used For Convenience