Not much to say here except that it works better than the collar that goes with any shirt. Who wouldn't want some metal instead of flimsy plastic? It doesn't even work with metal detectors, in case that matters to you. Perhaps you work in a courthouse or at an airport. Either way, different sizes actually come into play with different shirts. Yes, you wouldn't believe it, but that's how it is. They fit perfectly into the collar slit and give the shirt a neat look. For your health.