A handle height adjustment device of a handle assembly (2) of a walk-behind power tool (1). The handle height adjustment device (100) comprises a first toothed disk member (200), a second toothed disk member (300), and a disk interconnecting member. The disk interconnecting member (400) is arranged to be connected to the first toothed disk member (200) by means of a first interconnection mechanism (401), which first interconnection mechanism (401) inhibits relative movement between the disk interconnecting member (400) and the first toothed disk member (200) along an axis of rotation (500) of the handle height adjustment device (100), and which first interconnection mechanism (401) allows the disk interconnecting member to rotate relative the first toothed disk member about the axis of rotation (500). The disk interconnecting member (400) is arranged to be threadably connected to the second toothed disk member (300) by means of a second interconnection mechanism (402). The application also concerns a handle assembly and a walk-behind power tool comprising such a device.
