i use them on a lot my bikes, hate star nuts.
they work by having one spacer like a cup and one like a cone but split, which has a grub screw to push the split open (you can see the bits on the pics) this expands the cone and pushes the cup upward. (or the cone down
so you need to clamp the stem on full first and have the headset quite tight, then turn the screw to tension the headset up. that make any sense?
they are supposed to make it easier if you change forks alot (or frames in my case) which they do, but they have one problem which is durability.
the rings are alloy, but the grub screw is steel, so it bores into the alloy over time and the grub doesnt expand the cone as much. they should put a brass plate in there or something. wouldnt be a problem if you dont adjust it a lot, but the thats half the point of it, to take on and off easy. also pretty sure the alloy stays a bit expanded afer a while so it needs extra expanding. i use a longer screw than the one they give, which sorts out both problems.
im not doing a great job of talking them up but, ive never had a failure they they look kinda cool too, which is the main thing