gas-thru length

[Magaholic]

I just added a flatline tank to my 68 classic and am looking to put a different foregrip on it. I've got my eye on either the new dye gas-thru or the system-x gas thru. I'm running the stock flatline drop right now. I'd like to know the lengths of these gas-thru grips minus the threads that screw into the asa. (basically the length from the shoulder just before the threads start to the bottom of the grip) I've emailed a couple of shops that have these in stock but haven't seen any responses from them. Does anyone have this info?

Thanks!