Hey, Al,
I have called TOTW but the rep wasn't totally sure. He said he hasn't seen this new underhammer model yet, so he offered his "guess" between two smaller wrenches TOTW has, what he thought might fit. It would have been a good thing if a wrench was included with the pistol. Seems like a small enough item to be included for the higher pistol cost. Ah, well.
PT7