HS4 Carb Jets

["Erik Brzoska" <mowog77@hotmail.com>]

I was just looking at the HS4 carbs I have just finished rebuilding and 
I was wondering something.

Some outfits sell rebuild kits with the same jets used for the front and 
rear carbs, but Moss and VB sell differing jets (front, rear)for the 
same rebuild kit. 
This specialized set of jets costs a lot more than the outfits that 
offer generic jets.

My question is, if both jets deliver the same amount of fuel and at the 
same rate, why do they have to be differentiated (front and rear)?

TIA
Erik.