Originally Posted by dabac

A BBB BHP-21.

A bigger Allen head bolt is used to pull the wedge up against a recessed wall in the stem. The tool socket is drilled and tapped for an M6 Allen, slightly longer than what's normally used to hold a top cap in place.

I've never seen one with the same bolt used for both wedge and top cap.

The one on my road bike doesn't even have a top cap screw. Top cap is simply press-fit, with an o-ring.