I just received my 4125/2 today. (26mm knot/55mm loft) I haven't lathered this beauty yet...that's tomorrow morning. A few things I've noticed: The logo is no longer on the side of the 4125 model. It's on the bottom. From the feel of this brush... it is going to have good backbone to lather those hard soaps. To me...it has plenty of 2-Band Silvertip Badger Hair for good density. Here's a few pics before it gets wet tomorrow.
I think moving the logo to the base of the brush is a better look in general and it really works with this one. You are going to enjoy this!
I'm afraid you've made a terrible mistake purchasing this brush. Immediately wrap it up and mail it to me. I will know how to dispose of it from here.