Flatbar handlebar Common Sizes

This post is about flatbar handlebar common sizes on commuter/urban/flatbar road bikes.

Flatbar or Riser ?
Flatbar is generally pretty straight.
Riser bar is the V-type shape.
For a commuter/flatbar road bike my preference would be flatbar.
So this post is about Flatbars.  

If you have a flatbar handlebar bike.
And want to buy a new flatbar handlebar.
You probably need to work out 2 main dimensions.

The 2 most important specs seem to be :
Stem size.
Width (across)

Flatbar common Stem sizes :
Importance : I think very important (if you can't adjust the fitting for the handle-stem joint.)      

The 2 common flatbar Stem Sizes :
25.4mm (standard)
or 31.8mm (oversized)

There are other sizes but these are the common 2 sizes
Tip :
If your handlebar in the middle looks 'normal sized', it's probably 25.4mm
If your handlebar looks overly big in the middle, it's probably 31.8mm 

Common flatbar widths (across)
Importance : not so important  (?)

Typical flatbar widths :
600mm ?
580 mm would be pretty small.
620mm gives you a bit more space .
The width can go up to 750mm

Note : Riser bars seem to have much wider lengths, such as 750mm
I have read that bars can come big in order to 'saw to size'