Took my dial indicator and built a tip opening gauge similar to the one sold by Theo Wanne. I then measured a few of my alto mouthpieces and found that some of them varied considerably from those published by manufactures and those found on various tip opening charts. For example the published tip opening for a Selmer C is 62. My Selmer C measured 54! The published tip opening for a Selmer C* is 65. My Selmer C* measured 60. the published tip opening for a Rico B5 is 95. My B5 measured 73! The published tip opening for a Rico B3 is 83. My B3 measured 67. Wow, quite a difference. The only one that was right on the money was the cheepo Gigliotti Spectrum tenor mouthpiece that I recently purchased. It was advertised on eBay with a tip opening of 67, and low and behold, mine is right on 67!!!