The Tip Opening
The tip opening is the distance between the tip of the mouthpiece and the tip of the reed. So, when you are assembling your mouthpiece, you place the flat part of the reed against the flat part of the mouthpiece, called the table. Matching the arch of the mouthpiece of the reed to the arch of the mouthpiece, that little gap is the tip opening. On your mouthpiece, there will be a number etched into the side. The bigger the number, the bigger the gap between the mouthpiece and the reed.