Lightweight alloy Dynamo/Alternator pulley 75mm wide 2.95" and where belt sits 48.895mm (1.925")wide. Fits all Dynamos and 15mm Diameter shaft 16ACR Alternators.
Owing to the cost many use
12A1772 which is 79mm 3.1" wide -
12A34 was originally pressed steel and riveted. This has keyway slot whereas later type has no keyway and fits 18mm spindle.