Identifying Circular Needles

Hi Everyone,
I’m a knitting newbie. I have inherited a lot of circular needles from my mother. How do I identify the size they are? I’m looking all over the needles but don’t see any numbers. I’m sure my mom knew exactly what each one was. But I have no idea. Thank you in advance! :slight_smile:

There are sizers like this,

Thank you!!

This is the sizer I use. To measure length you measure from needle tip to needle tip.