if you can test the produce in their presence. You are a buyer. You should have the right to select your purchases by means other than simple appearance. Many consumers are conditioned to buy, whether they wish to or not, once they take a sample. Perhaps you should let the refractometer guide you to a "Thanks, but no thanks" when it indicates poor or average produce. Of course, you may (and probably will) decide to buy a considerable amount of any produce that tests either GOOD or EXCELLENT. However, you should never judge (nor "label") someone's produce as POOR or SO-SO. Simply tell the operator that you are looking for "higher sugar." Fruit stand operators have feelings, too. Remember that you are a consumer, not an arrogant inspector. And please remember that you have no desire to "punish" the stand operator for all the years of poor produce you have endured. You are trying to open channels so that you can get BETTER fruits & vegetables. Yes, you want this person interested in your special needs. Let the operator examine your instrument if they wish. Let them verify your readings. Ask how they select what they buy at the wholesale market. Ask if they can pick HIGH QUALITY produce out of a pile by its heft (a few experienced operators can). Many operators will be fascinated with your refractometer. Some may offer to buy it. They may quickly grasp how it could help them get better produce at the wholesale