What size is that needle? Hard to tell.

I really do not care. I knit swatches with different sized needles and then
use the needles that produced the fabric that I liked. If you want to do
better, get a micrometer and measure the actual diameter of your needles.
The traditional needle gauges with holes in them make errors in needle
naming easy.

Consider US # 1 needles. The holes in the "Boye" standard knitting needle
gauge and the "Susan Bates Knit Checker" have holes for that are just larger
than 2.50 mm in diameter so that the Boye and Susan Bates # 1 needles are
just under 2.50 mm in diameter and *just* fit in that gauge hole. However,
in the Knitter's Companion, there is a cardboard needle gauge that the hole
for #1 that is 2.25 mm in diameter, but the text in Knitter's Companion says
that US #1 is the same as 2 mm?!! Then, when I look at the needle size chart
in Mary Thomas/ Dover reprint, the diameter of the spots she provides in her
needle size chart do not match up with the diameters given in the text.
Moreover, my AddiTurbo needle sold to me as a US #1 is about 2.51 mm in
diameter, thus does not fit in the gauge holes for #1 needles. It is hard
to tell that it is just a little bit over and so and it must be a # 2?? : )

Skipping to the chase here.

Measuring my Susan Bates Knit Check (aluminum knitting needle gauge), the
sizes of the holes are as follows:
1 - 2.50 mm
0 - 2.25 mm
00 - 1.85 mm
000 - 1.50 mm

However, the sizes of the handmade steel needles that I use a
1 - 2.32 mm
0 - 2.00 mm
00 - 1.65 mm
000 - 1.20 mm
Which is about what you will get if you make your own steel needles from
music rod available in the American market. However, precise metric sized
spring steel rod is available on the world market.

Of course, you could make those size needles and rename them After all,
what I call a #1 is only 0.07 mm larger than SB's "0" but 0.18 mm smaller
than what SB calls #1, so by actual size it is much closer to being a "0"
than a "1". But, it fits in the "1" hole and not the '0" hole, so for me,
for now, it remains a "1". This why I say that hole based gauges introduce
real errors in needle naming.

The really bad news is that last night, I did gauge swatches on the cashmere
yarn that has been sitting like a lump in the middle of the stash, and this
morning at the breakfast table my wife said that the swatch from the 1.2 mm
needles is the best fabric. It is a lovely fabric, but that is a lot of
knitting. Maybe she would like matching hat and gloves rather than a
sweater.

Aaron