Alliance vs DW Ultra

[Lario]

Hi, we all know that the Alliance measure 4 corresponds to DW measure 5. We also know that the Alliance mouthpieces are identical to DW Ultra series. Alliance for that measure offers two mouthpiece, 4 and 4A. DW serie Ultra only one the SM5U. I wanted to know which of the two Alliance matches the SM5U. Thank you all for any replies.

[Fishlips]

Just from looking at the manufacturers websites, it appears that the difference in specs relates to rim width. The SM5U has a width of 6.3mm, whereas the Alliance 4 is listed at 6.73mm and the 4A at 6.78mm. I don't have any of these particular mouthpieces, however, and will leave it to others to discuss any potential differences in rim shape, cup depth, backbore, etc.

[Lario]

Thanks for the reply. The main difference between Alliance 4 and 4A is the depth of the cup I would like to know which of the two corresponds to the SM5U