Nico: Thanks to claxton for that link. I took a quick look at it but did not see a facings' chart. Maybe I just missed it. Good resource, though.
Basically, mouthpiece makers use various methods to show the tip-opening on their pieces. Selmer uses a letter system, Link uses a number system. Both systems usually identify the tip-opening from small to large; e.g., a Selmer C* is more closed than an F; a Link 6* is more closed than an 8*, etc. The asterisk merely denotes a slight increase in tip-opening over the basic letter or number.
There are charts around that show what each maker's designations equal in inches or milimeters. Sorry, I don't have a link to one of those, but the WW&BB seasonal catalog has the charts - for most saxophones and clarinets.
Other factors not so well charted (if at all) are chamber sizes, baffle design, mouthpiece length, etc. All of those factors make a difference but there is no consensus as to exactly what combination is best for the reasons I cite below.
As to making a mouthpiece recommendation to you, many try to do that and I fear sometimes (often?) miss the mark only because what works well for them may not not work well for you. I've tried mouthpieces that others raved about and walked away wondering what they were thinking. When I think that everyone has a different embouchure, tonal goals and playing styles, then I realize that there is no ONE mouthpiece that most players will like.
Most of us did the field work ourselves (sometimes at great expense) to arrive at what we like best. I suspect you will have to do the same - there rarely is a quick-fix for your situation. DAVE