Drug info - Average size of blotters?

[I_Play_Stepmania]

So this guy that I know has done lsd before, quite a few times. He's done blotter, windowpane, and liquid.
The thing is when he used to buy blotter he'd just get it from another guy who would sell him his doses
already cut into doses. He recently bought a 10 strip of lsd and this is something he hasn't done before.
He was wondering if there was a general rule of thumb to how long a 10 strip should be? The guy my friend got this
from seemed a little sketch and my friend just wants to make sure he's not getting ripped off. From what he's
come to understand he asks the question: aren't all sheets that are used for blotter the same size so a ten
strip should be consistently the same length?

My friend is very grateful.