never used one are these used instead of the star nut and are they any good?

Yes and yes

oh yes

They are fine – if completely un-necessary over-engineering

what Druidh says.

PITA I say.

Whats wrong with a star nut?

oh god here we go – They do the job fine and dont score the inside of the steerer tube but SFN also do the same job – I prefer Head doctors but your free to use either 😉

I think the original use for the HD was for when the SFN scored the tube so badly it didn't grip no?

whooooaaa be carefull. Once split a steerer tube because of one. loosened stem pinch bolts and turned bars 90 degrees for transportation in a van and crack. Maybe a little operator error but word of warning. Don't over tighten or do what I did without loosening top cap. It wouldn't of happened with a sfn. All sorted with fox warranty any hoo.

They're OK, but SFN works just as well and is both lighter and cheaper.

Both equally as good but a SFN is easier to cock-up on installation. Whilst it's possible to install a SFN without a proper tool, it is prone to error.

A head doctor just requires an allen key.

And don't worry if the O ring gets torn/split. It makes little difference. A tiny drop of oil rubbed on the O ring will make it easier to install.

Cheers guys looks like i'll give the head doctor a go on my new ragley mmmbop

Careful with the topcap screw, it's made of an aluminium/cheese alloy and very easy to overtighten and snap.

Lactic – Member

Careful with the topcap screw, it's made of an aluminium/cheese alloy and very easy to overtighten and snap.

If it came with a 1.5" reducer headset it will have a stainless bolt. (Mmmbop has a 1.5" head tube.)