A shaft is not compatible just because its diameter matches. Joint thread and pilot geometry, seating depth, length and balance all matter.
Joint system
Match the thread name and pilot shape, then measure diameter and seating depth. Never force a part into resistance; repairing a damaged butt joint costs more than returning a wrong shaft.
Feel and balance
Even a thread-compatible shaft changes weight, stiffness and balance point. Ask for actual weight, length and tip specification, then hit test shots before committing to the fit.
Safe verification
Keep the original shaft until testing is complete, inspect both ends for cracks and require a return option if dimensions differ from the listing. Non-standard systems deserve a technician's measuring tools.