A Caphead is a threaded fastener with a socket head that is driven by an Allen Key / Hex key.
Normally grade 12.9 unless they are stainless steel when the grade is stated as A2 or A4.

These are not all fully threaded, the rule of thumb for the amount of thread is NORMALLY 2 x the diameter + 1/2 an Inch.

To measure a caphead, you measure the length underneath the head.
Just because the caphead is the same diameter as yours does not mean it is exactly the same. The ones listed here are all Metric Coarse thread.
Occasionally in engineering and automotive industries they use a finer pitch on a caphead. While we do not stock these, we are normally able to get hold of them,
Contact us for a quote!

Also, please bear in mind there are several different metric fine pitches, for example;

M10 x 1.5 = Standard/Coarse
M10 x 1.25 = Fine
M10 x 1 = Extra Fine

Please ensure you are asking for the correct pitch and be aware that there are minimum order quantities for non-stock items.