An alignment gauge is essential for diagnosing and repairing bent or misaligned derailleur hangers, often the source of shifting problems.
Park Tool DSD-2 Derailleur Screwdriver - one size
Park Tool Valve Core Tool VC-1
Park Tool CT-5 Mini Chain Brute Chain Tool
Park Tool BBT-9 External Cup Bb And Hollowtech II Tool
Park Tool CT-3.3 Professional Chain Tool
Park Tool I-Beam 3 Multi Tool IB-3