RichSPK- When I bought mine a few years ago they had two sizes. The small one that they sell now is smaller than a dime. The larger one was the size of a nickel. I much prefer the small one. It just takes a little while to find the right spot on the helmet. I bought a bag of similar magnets on eBay and played around with them for a while. Hot glue is your friend here. The only annoyance is you sometimes have to reposition it after removing your sunglasses. It's hard not to bump it in the process. But it is easy to reposition.