What is B Grade merbu

Hey Guys,
How do they rate merbu?...I am looking at some and it says "B Grade Merbu 90x19"

I know 90mm is the width, but what i the 19? Sorry if this seems like a stupid question but I just dont know.

: )

19mm thick.

Don't have the experience to answer the "B Grade" part.

Ah...Dont know why I didnt think of that. Thanks...

Not aware of any 'standard' rating scheme. I reckon it's just rejects. I'd want to look at it first.

It is usually graded at the mills.
B grade would have mould (which apparently can be cleaned off), marked/scratched etc.
You could have a close look at the wood. If you know what to look for and can select your pieces (most places don't like this!).
I s'pose the most important is to ensure it is straight and not warped and is dried.
In my recent experience you get what you pay for.
If it's too good to be true (the price) then it usually is.