The synchro ring for the Citroen HY 67-/ID 64- is a crucial part of the gearbox. This ring ensures a smooth transition between gears by synchronizing the rotational speed of gears. It prevents wear and extends the lifespan of the gearbox. It is specifically designed for older models like the Citroen HY from 1967 and the Citroen ID from 1964. Replacing this ring can significantly enhance driving experience and provide a quieter, more efficient vehicle operation.