The stub ends of the boom front end are 26mm O.D., intended for Aeron booms of 29mm OD with 4 screw detachable arms.
They will also fit a number of other booms of similar design from companies like Naish, Pro Limit from the period around 2002 onward's, but please try and get your boom apart and check dimensions first to make sure and drop us an e mail to seek advice?
To get old booms apart, soak in hot water several times to dissolve the salts and apply penetrating lubricant over several days, so you do not wreck the screws getting your old one apart.