I remember reading about this a few years ago. It seems like a decent idea but the price is just a bit off-putting. I just looked at the website. I see it's $125. If I'm reading the pictures right, it's a replacement headset where the top nut includes an extension that simulates an unthreaded steerer tube. So I wonder, is that extension attached to the original steerer tube by just the threads? That seems like a less reliable connection than a threadless stem adapter.