4.52 Bore, Very nice example ofMartin Imperial, sounds and plays amazing, sounded similarly rich and complex, held itsown when pitched, even a bit darker (better than the latter day Committees). Nice and smooth downstairs and lightsup when pushed. Sounds just like a proper Martin. Cleaned, it's fully serviced,new felt pads, corks, valves and slides work like a dream, Great compression, it's fullyfunctional. please feel free to send me a message.