This ligature seems just slightly small for most modern clarinet mouthpieces. I do believe it is for a key of Bb clarinet mouthpiece, but perhaps one with a slightly slimmer than normal body. The interior dimensions are approximately 25mm wide by 28mm high. That is taken at the back of the ligature, with its screws fully tightened. Obviously, it can open up from there, but that is as tightly as it will close. Hopefully this will help you in determining whether this will fit your mouthpiece.
This ligature is in excellent condition. It has not been bent out of shape. There are no stress cracks. The screws work properly. The nickel plating shows light wear and scratching. Also included is the original metal cap for this ligature. It is in good condition with no cracks or dents.
Please feel free to message me with any questions.
Thanks again for looking!
06/29/25-1-G