A replacement crank arm magnet for the garmin GSC10 cadence sensor. It should work with any other magnetic cadence sensor. The default magnet is a 1/4"x1/8" (diameter x height) rare earth magnet. You can customize the design for any size but you'll have to convert to mm. See instructions for assembly and customization notes.The magnet should interference fit into the part, so make sure you don't choose a magnet diameter that's much too big (diameter+0.2mm worked well for me). I recommend ABS as it's softer but PLA should work if you increase the magnet diameter a little (~0.3-0.4 vs ~0.2) to account for PLA's hardness/brittleness. You can also glue the magnet. These are the magnets I used (not affiliated w/ them). http://www.magnet4less.com/product_info.php?cPath=1_11&products_id=100 Assembly: Optionally, you may plastidip after step 2.