I have tried these wurkin stiffs collar stays on 2 dress shirts so far after receiving them, and they work perfectly at holding the collar tight to the shirt. I am extremely fussy about my collars. I like a stiff collar that stays upright against my shirt, and these collar stays do the job. I have tried them on both "non-iron" and soft supima cotton dress shirts, and they work beautifully on both. The magnets are very strong.
My only complaint so far is that the magnetic buttons that go on the inside of the shirt collar are visible from a side view when wearing a dress shirt without a tie and the top 2 buttons unbuttoned. I haven't had anybody comment that they see them, but I can see them in the mirror when looking directly at that area. They are small and high-quality looking though, so they could pass for an inner styling detail of the shirt.
My previous way of dealing with collars was to iron them the night before, then immediately put clothes pins on them until the next morning so that they kinda "molded" tight against the shirt. This technique worked well, but I think I like these collar stays better.