Started building my tripster today and cut the steerer down. Was (tentatively) about to knock a star nut into the carbon fork. I think rather fortunately I then spotted this;

looks like some kind of carbon steerer-safe headset tightened thingamajig. Can anyone tell me if I’m right and how to use it? I couldn’t figure it out if it is.

Please don’t use a SFN 🙂

You do indeed need to use that bung. Pop it in the steerer, tighten the bolt with an allen key which will expand it so that it grips the steerer. Fit stem / topcap as normal.

Cheers, that’s what I thought but couldn’t get it working but El persevere now I know 🙂

Can’t tell you how lucky it was to find it by chance as I was about to strike the hammer!