If you buy the less expensive ones.... and doing a Google search will show you companies that charge alot of money for them... then if they don't work for your particular discomfort, it is no loss really. If you spent hundreds of dollars on a belt or mattress etc, that would be a shame if they don't work.

The size I used on my knee is 1/2 inch wide and 1/16th thick.
Those were a decade ago now!

The best placement was on the meniscal trigger point...which the orthopedic doctor demonstrated to me was my hot spot.

The really large magnet I use now, I tried on the back of the knee where I put my Lidoderms sometimes, and it made my lower leg "buzz" for some reason. I don't know why that is either.

I did use my 1/2 inchers on my thumb with the torn nail...and at the base of the thumb it stopped my throbbing (which was awful!) I used the tiny ones on my broken big toe, back when the boulder rolled out onto it. (I had to take it off for the x-ray at the foot doctors when that happened).

For when my feet really burn and sometimes that goes 1/2 way up my shins, I use Biofreeze for that. Avoiding potatoes gives me less incidence of that in the past year. Really hot summers, can make burning nights for me still too anyway.

So using the Ebay sellers is best. Just type in "neodymium magnets". If you want the plastic coated ones, like plgerrard, then put "plastic coated" in the keyword too. I find that links to companies on Google keep changing. And some magnet suppliers won't deal with you if you want smaller amounts of them and charge a surcharge for the order. Ebay does not, and some even have free shipping every once in a while!