Quick collete question.

Hey guys.

I have a quick question.
We have a broken collet.

The outside largest diameter is about 1.03 and the length is 2.01.
So heres the question. Online I found ER25 colletes to be 1.02 diameter,
but they are very short. Does tht length mater?

What I found was 1.02 dia x 1.38 long. not 2.01 long.

How do I know what series of collet we were using?

PS : this is not for a cnc its for a manual mill, not sure that makes any difference.

Thanks