250mm or 10"

11" from end to end.

I bought the meter to do just that for a brandy that I make. I have not had the chance to use it. Most of my readings on the subject indicate that sugar affects the accuracy. So I think if you use it as a comparative devise like I plan to you would be able to view consistency in your wine.

No alcoholmeters should be used to measure distilled spirits because they measure ethanol in water. Hydrometers are used to measure fermented products like beer wine and cider because they measure sugar content. They are mutually exclusive measurements.