Bellini Fixer F5 is formulated to the Kodak specification of the specific fixer for Double-X, negative film 5222, 7222.
The same processing formula using D96 developer and this fixer is recommended by Orwo for their superb N74 and UN54 films.
Kodak give specific indications to use fixer F5, as it is not easy to fix these films to their standards.
Mix parts A + B together to give one litre of working solution yielding up to 30 films or more per litre.
You will also find this offered by Nik & Trick as a package with some film and the D96 developer