A key for use in a cylinder lock with a rotatable key plug having an elongated key blade with a relatively wide lower portion and a relatively narrow upper portion. A step-like transition region between the wider lower portion and the narrow upper portion. The key blade includes a longitudinal profile groove located adjacent to the step-like transition region that extends along at least a portion of the length of the blade. An inner wall of groove is substantially parallel to a side surface of the lower portion of the key blade. The longitudinal profile groove includes an undercut portion adjacent to and inside a ridge portion of the key blade. The outside of ridge portion forms a part of the side surface of the blade in the relatively wide lower portion up to the step-like transition region and the inside of ridge portion facing inner wall of the groove.

A key for use in a cylinder lock with a rotatable key plug having an elongated key blade with a relatively wide lower portion and a relatively narrow upper portion. A step-like transition region between the wider lower portion and the narrow upper portion. The key blade includes a longitudinal profile groove located adjacent to the step-like transition region that extends along at least a portion of the length of the blade. An inner wall of groove is substantially parallel to a side surface of the lower portion of the key blade. The longitudinal profile groove includes an undercut portion adjacent to and inside a ridge portion of the key blade. The outside of ridge portion forms apart of the side surface of the blade in the relatively wide lower portion up to the step-like transition region and the inside of ridge portion facing inner wall of the groove.

A key for use in a cylinder lock with a rotatable key plug having a profiled keyway. The key comprises an elongated, substantially flay key blade (120; 120) having a longitudinal profile groove (122; 122) extending along at least a portion of the length of the key blade. The groove has an undercut portion (129) adjacent to a ridge portion (128, 128), the outside of which forms part of a side surface (123; 123) of the key blade. The undercut portion (129; 129) of the groove is expanded, at its innermost part adjacent to and inside said ridge portion, into a longitudinally extending pocket (135; 135).