I still use the refractometer I got when I was born. My eyes and hands. If I see that the vegetables or fruit rot, then I know that then can't be that good. If I see that vegetables and fruits don't rot after a week and are still crisp and not limp to the touch or when you break them, they I know that it was a good buy. I now buy the vegetables that look like the day I bought them after one week and the fruits that are juicy and not dry inside.