I recently purchased a Ted Klum London Model baritone saxophone mouthpiece in a .112 tip opening. I've been playing it for about 2 weeks now and am really satisfied with it. I've found that the mouthpiece speaks very quickly and clearly. The response is even across all registers and the low register, in particular, is very easy to play. The mouthpiece is also very reed friendly, which is really important to me. It's good to know that I'm going to have more reeds per box that are going to sound good.
The design of the mouthpiece is similar to a hard rubber Berg Larsen with a bullet chamber. In Berg terminology, this mouthpiece would probably be like a 112/0. The mouthpiece is metal (mine is bronze), but is the same size as a hard rubber piece. This makes it probably the heaviest mouthpiece I've ever seen - not a good or bad thing, but just an observation.
The mouthpiece is expensive at $775, but as a professional, I have no doubt that it will pay for itself over and over.