Cateye's wheel magnet has been a popular replacement magnet. If you have a round or bladed steel spokes on your wheel, this magnet offers a secure hold for either type. The magnet carrier has a screw post that threads into the receiving plastic housing. On either side of the receiver you will see distinct sides- one recessed with a rubber non-slip pad for round or slightly oval spokes, and the other side is flat, for wider bladed spokes. You simply choose the side required, press it against your selected spoke, magnet side out towards your sensor, and screw it into place. Once firmly threaded, the magnet will stay affixed. There is no need to over tighten or use tools. If you need to adjust the location, just loosen the magnet and slide the unit into place, then re-tighten. The magnet can easily be moved from wheel to wheel or removed if desired with no fuss.

In general, exceptionally wide spokes from Mavic and Fulcrum aren't a great fit, but virtually every other spoked wheel is compatible. Most computer systems and sensors use standard magnets like this Cateye version, but some require special magnets. Please check with the computer or sensor manufacturer for requirements.