Help a daftie figure out what size stem he has

[veganhaggis]

I've tried googling this, read various articles etc but I'm struggling to wrap my head around this and be absolutely sure.

The stem is marked with 28.6, I measured it last night with some calipers and it is closer to 27.9mm in reality.

So that would make this a 1 1/4" stem?

It's too big to be a 1 1/8" (which fits inside a 28.6mm steerer... no wonder I'm confused )

 

[foz]

Yes that will be for a 1 1/4" steerer. The difference between the outer diameters of a 1 1/4" steerer and your 28.6mm (1 1/8" in imperial) is 1/8", which divided by 2 gives a tube wall thickness of 1/16", which is standard for steel tubes.