Engine anodes usually consist of a
replaceable zinc pencil and a
separate brass plug

Dimensions are usually given as length of body x diameter.

The threaded part is extra and defined by
it's diameter and the thread name. Measurements are
in turns per inch (tpi) for Imperial or 'the pitch' (distance between one turn and the next) for metric threads.

VW , Beta and other engines have a large variety of screw in anodes. If our die cast anodes will not fit we can usually make others from rod stock. Alternatively replace the brass plug to take the cheaper die cast anode.
See also Bukh, Petter and Yanmar