Each select field has a different set of options even the same select list may have different set of options for different field contexts (pair of project and issue types). Sometimes you may need to add the same set of options to several different select fields and each time when you need to change it may be difficult to add them one by one to each select field. By using database synchronization feature of "Single Select++", "Multi Select++", "Radio Button++" fields you can greatly reduce effort required share set of options between different select custom fields. Just setup each select custom field to synchronize with the same SQL Query and you have done. Each one will update themselves from the database periodically.