If your Ultra forearm is a cinnamon color it should work fine, the barrel diameter should be OK....but if you have the extra $ then get the extra forearm, they will match the color as a set when they send it out. There could always be a bit of a difference, there should not be but there could be....Also, its always nice to have a another stock "set"....<><....
P.S. just a hint, when you order them ask them if they have any checkered sets available (if of course you want them), they sometimes have one or the other, or both available, ask for everything, you might get part of what you ask for!!!! :-D