Small eliptical "football*" shaped winding key is a replacement for most Wittner 820, 830 (Piccolo) and 880 (Piccolino) and 829161 metronomes that originally had this style of key. If your Wittner had a "ring" style key, this one may not work, as the shaft may be too short. IN that case you may want our part number 0255546. Wittner replacement part number 410 060 008.
* as in American football - not European football (aka "soccer").