How to measure gearbox Bearings?

As title says I need to buy a gearbox bearing kit for my shitvic as me and Stu call it (civic em1 vti) basically there 2 kits the only thing that changes out of both kits is the diff bearings are different one kit being 18mm and other being 19.5mm and I just want to know how to measure this (what part of the bearing)  I think there 18 mm

Here's photos Stu in uploading them for me with my finger on the bearing I think it's the width of bearing personally

Cheers Stu

It wont be the outer diameter as that would be far bigger than 18mm

Not unless its the depth ?

I haven't a clue nomad lol I reckon it's how I have placed my finger on first photo but just wanted to be sure as ordering it from UK and could do with out a F**k up lol

Don't on bearings use 3digit numbers
Measure inside diameter,outside diamiter and thickness

Johnny is correct, if you look on the side of the bearing there will be an alpha numeric code as well as the makers mark e.g NTN or NSK, this is all you need to quote when ordering from a bearing supplier mate.

I remember arguing with someone as I wanted a 370 deg bearing he was convinced there was no such thing as a circle was 360 I said it is the heat rating he looked at me like I was stupid

All roller bearings have 3 key dimensions, bore diameter, outer diameter and overall width.
Hope this helps.

it the width of the race (in this case width of inner race I think, 19.5mm bearing is NTN special made for honda)
If in doubt just google your diff NTN bearing numbers and you should find the answer as common info for honda lovers .

Cheers Mr B