This adapter sleeve provides a mounting interface between a shaft of standard tolerance and a bearing with a tapered bore, allowing the bearing to be fitted on cylindrical seating without the shaft itself being ground to a taper. It has a bore diameter of 25.0 mm, a net mass of 124.49 g, and a standard design, designated H2306. Tightening the sleeve draws the bearing inner ring up the taper, generating the radial internal clearance reduction needed for a secure fit and allowing axial positioning to be adjusted along the shaft during mounting. This construction simplifies dismounting compared with a directly interference-fitted bore and is suited to applications where a self-aligning bearing with a tapered bore is used on plain shafting.