Tip openings are usually measured in thousandths of an inch. Example: A Size 7 Tenor Mouthpiece would be around (.100 thousandths of an inch). When a saxophone player asks me what tip opening should they play? My answer is, play what's most comfortable for you to achieve your sound. Why make it harder on yourself? There is a misconception that says, if you play a larger tip opening and stiffer reed, you are a better player. This is entirely incorrect! Some of the best saxophonists of all time like John Coltrane, Charlie Parker, and Dexter Gordon played on smaller tip openings. If you are a beginner, a smaller tip opening is typically easier for the purpose of control and lack of embouchure development. Enjoy playing, don't make it to difficult on yourself. Feel free to email or call me at 951-805-5611 to discuss the best opening for you.