this magnet unit carries a square magnet internally or externally.
Magnet dimensions are 10mmm x 10mm x 2mm.
IF you want to mount the magnet externally, you need to use a magnet with a mounting hole similar to the one in the photo.
![NdFeB Channel Magnet w/ Countersunk Hole - Magnets By HSMAG | Magnets, Neodymium magnets, Phone ring](https://i.pinimg.com/originals/71/77/a3/7177a3c446071e936a4eda85f53f75a1.jpg)
or use a magnet like the one below and store it internally. But the intensity of the light generated is more when the magnet passes closer to the pickup coil.
![N52 Super Strong Neodymium Block Magnet 2x2x1/2” Flat NdFeB Rare Earth Rectangular Magnet for Science, Projects and Industries, 1-Count: Industrial Rare Earth Magnets: Amazon.com: Industrial & Scientific](https://images-na.ssl-images-amazon.com/images/I/61%2BzG0L0NFL._SX342_.jpg)
![](https://www.endtas.com/wp-content/uploads/2021/05/image-152-1024x574.png)
![](https://www.endtas.com/wp-content/uploads/2021/05/image-153-1024x574.png)
![](https://www.endtas.com/wp-content/uploads/2021/05/image-156.png)
if you like there is a much smaller version of a magnet holder on
my thingiverse page. Click here to go to that page.
![](https://www.endtas.com/wp-content/uploads/2021/05/image-157-1024x621.png)