These work as expected. They keep the collar straight and the weight of them keeps the collar from flying around. Much better than plastic collar stays. They're thick enough that they won't bend easily. Having 4 different sizes means they should work for most shirts and you don't have to worry about getting the correct size.

My only issue with them is that it would have been nice to know what type of metal was used for them. I tried contacting the seller and received no response.

There are other stainless steel collar stays on here for not too much more. If I were purchasing again I'd probably go with those. As I said, these work fine but without knowing what type of metal and/or plating I'm not sure if these will wind up corroding at any point in the future. These might be nickel but I'm not sure. They will stick to a magnet but stainless steel attracts magnets better. If you plan to use magnets to hold the collars down I'd go with ones that specifically say they are stainless steel just to be safe.