A dose setting mechanism (4)for a drug delivery device(1) is disclosed. The mechanismcomprises an outer housing (40) and aninner housing (44) having an externalgroove (62) and a helical spline (68).The inner housing helical splineguides a driver (30) to dispense a setdose. A dial sleeve (10) is disposedbetween the outer and inner housingand is rotatably engaged with the innerhousing. When a dose is set, thedial sleeve is rotated and translatesaway from both the outer housingand the inner housing.
