BBB has an internal stem Riser part # BHP-21, as an aluminum Quill it will reinforce the steerer tube,
somewhat .. the top cap still does the headset pre-load thru the spacers beneath it
US distributors : Bike Mine In OKC, I got mine thru R&E in Seattle,
but any shop that has or will open a Bike Mine parts distributor's account
can order it..

I expect the steerer tube is aluminum on a CF fork as cutting grams sells
to the weight, less = better, crowd.
Magnet will tell of course..