These are different than the other 8mm collets Dad used - are they special purpose of some sort? They are a boxed set of 17 (Levin) , marked 14 thru 30.
Metric I assume?

pic 2

Hi Kevin,

Looks like jewel collets, just sold a set myself here recently different make. Looks like the center rod slides in, my set screwed to get depth

Thanks Chris !